diff --git a/libs/container/container.h b/libs/container/container.h
index 67e83b67..e13d5ab9 100644
--- a/libs/container/container.h
+++ b/libs/container/container.h
@@ -25,6 +25,7 @@
 #include <set>
 
 #include "generic/static.h"
+#include "debugging/debugging.h"
 
 /// \brief A single-value container, which can either be empty or full.
 template<typename Type>
@@ -56,111 +57,199 @@ public:
 };
 
 
-/// \brief An adaptor to make std::list into a Unique Sequence - which cannot contain the same value more than once.
+/// \brief An adaptor to make std::set or std::multiset into a SequenceContainer.
 /// It's illegal to modify inserted values directly!
 /// \param Value Uniquely identifies itself. Must provide a copy-constructor and an equality operator.
-template<typename Value>
+template<typename Value, bool UniqueValues>
 class UnsortedSet
 {
-	typedef typename std::list<Value> Values;
-	Values m_values;
+	struct Node
+	{
+		Node *m_prev;
+		Node *m_next;
+		Value m_value;
+		Node( const Value& value ) : m_value( value ){
+		}
+		static void link( Node *prev, Node *next ){
+			prev->m_next = next;
+			next->m_prev = prev;
+		}
+	};
+	/// special thin sentinel node to avoid DefaultConstructible \param Value requirement
+	struct SentinelNode
+	{
+		Node *m_prev;
+		Node *m_next;
+		SentinelNode(){
+			selfLink();
+		}
+		void selfLink(){
+			m_prev = m_next = asNode();
+		}
+		Node* asNode(){
+			return reinterpret_cast<Node*>( this );
+		}
+		const Node* asNode() const {
+			return reinterpret_cast<const Node*>( this );
+		}
+	};
+	static_assert( offsetof( SentinelNode, m_next ) == offsetof( Node, m_next ) &&
+	               offsetof( SentinelNode, m_prev ) == offsetof( Node, m_prev ),
+	               "Node layouts must be compatible for reinterpret_cast" );
+	SentinelNode m_end;
+
+	template<bool IsConst, bool IsReverse>
+	class Iterator
+	{
+	public:
+		using iterator_category = std::bidirectional_iterator_tag;
+		using value_type        = Value;
+		using difference_type   = std::ptrdiff_t;
+		using pointer           = std::conditional_t<IsConst, const Value*, Value*>;
+		using reference         = std::conditional_t<IsConst, const Value&, Value&>;
+		using node_ptr          = std::conditional_t<IsConst, const Node*, Node*>;
+	private:
+		node_ptr m_node;
+	public:
+		Iterator( node_ptr node = nullptr ) : m_node( node ){
+		}
+		reference operator*() const {
+			return m_node->m_value;
+		}
+		pointer operator->() const {
+			return &m_node->m_value;
+		}
+		Iterator& operator++(){
+			if constexpr ( IsReverse )
+				m_node = m_node->m_prev;
+			else
+				m_node = m_node->m_next;
+			return *this;
+		}
+		Iterator& operator--(){
+			if constexpr ( IsReverse )
+				m_node = m_node->m_next;
+			else
+				m_node = m_node->m_prev;
+			return *this;
+		}
+		Iterator operator++( int ){
+			auto ret = *this;
+			++( *this );
+			return ret;
+		}
+		Iterator operator--( int ){
+			auto ret = *this;
+			--( *this );
+			return ret;
+		}
+
+		friend bool operator==( const Iterator& lhs, const Iterator& rhs ) {
+			return lhs.m_node == rhs.m_node;
+		}
+
+		// Conversion from non-const to const iterator
+		template <bool OtherIsConst, bool OtherIsReverse>
+			requires ( OtherIsConst && !IsConst && ( OtherIsReverse == IsReverse ) )
+		operator Iterator<OtherIsConst, OtherIsReverse>() const {
+			return Iterator<OtherIsConst, OtherIsReverse>( m_node );
+		}
+	};
+
 public:
-	typedef typename Values::iterator iterator;
-	typedef typename Values::const_iterator const_iterator;
-	typedef typename Values::reverse_iterator reverse_iterator;
-	typedef typename Values::const_reverse_iterator const_reverse_iterator;
+	using iterator = Iterator<false, false>;
+	using const_iterator = Iterator<true, false>;
+	using reverse_iterator = Iterator<false, true>;
+	using const_reverse_iterator = Iterator<true, true>;
+
+	iterator               begin()        { return m_end.m_next; }
+	const_iterator         begin()  const { return m_end.m_next; }
+	iterator               end()          { return m_end.asNode(); }
+	const_iterator         end()    const { return m_end.asNode(); }
+	reverse_iterator       rbegin()       { return m_end.m_prev; }
+	const_reverse_iterator rbegin() const { return m_end.m_prev; }
+	reverse_iterator       rend()         { return m_end.asNode(); }
+	const_reverse_iterator rend()   const { return m_end.asNode(); }
 private:
 	struct Compare{
 		using is_transparent = void;
 
-		bool operator()( const const_iterator& one, const const_iterator& other ) const {
-			return *one < *other;
+		bool operator()( const Node& one, const Node& other ) const {
+			return one.m_value < other.m_value;
 		}
-		bool operator()( const Value& va, const const_iterator& it ) const {
-			return va < *it;
+		bool operator()( const Value& va, const Node& node ) const {
+			return va < node.m_value;
 		}
-		bool operator()( const const_iterator& it, const Value& va ) const {
-			return *it < va;
+		bool operator()( const Node& node, const Value& va ) const {
+			return node.m_value < va;
 		}
 	};
-	std::set<const_iterator, Compare> m_set; // store sorted iterators for fast lookup
-	void init_set(){ // only load set, when lookup is needed
-		if( m_set.empty() )
-			for( const_iterator it = begin(); it != end(); ++it )
-				m_set.emplace( it );
-	}
+	std::conditional_t<UniqueValues, std::set<Node, Compare>, std::multiset<Node, Compare>> m_set;
 public:
-
 	UnsortedSet() = default;
-	UnsortedSet( const UnsortedSet& other ) : m_values( other.m_values ), m_set(){
-	}
-	UnsortedSet( UnsortedSet&& ) noexcept = default;
+	UnsortedSet( const UnsortedSet& other ) = delete;
+	UnsortedSet( UnsortedSet&& ) noexcept = delete;
 	UnsortedSet& operator=( const UnsortedSet& other ){
-		m_values = other.m_values;
-		m_set.clear();
+		clear();
+		for( const auto& value : other )
+			push_back( value );
 		return *this;
-	}
-	UnsortedSet& operator=( UnsortedSet&& ) noexcept = default;
-
-	iterator begin(){
-		return m_values.begin();
-	}
-	const_iterator begin() const {
-		return m_values.begin();
-	}
-	iterator end(){
-		return m_values.end();
-	}
-	const_iterator end() const {
-		return m_values.end();
-	}
-	reverse_iterator rbegin(){
-		return m_values.rbegin();
-	}
-	const_reverse_iterator rbegin() const {
-		return m_values.rbegin();
-	}
-	reverse_iterator rend(){
-		return m_values.rend();
-	}
-	const_reverse_iterator rend() const {
-		return m_values.rend();
-	}
+	};
+	UnsortedSet& operator=( UnsortedSet&& ) noexcept = delete;
 
 	bool empty() const {
-		return m_values.empty();
+		return m_set.empty();
 	}
 	std::size_t size() const {
-		return m_values.size();
+		return m_set.size();
 	}
 	void clear(){
-		m_values.clear();
+		m_end.selfLink();
 		m_set.clear();
 	}
 
 	void swap( UnsortedSet& other ){
-		std::swap( m_values, other.m_values );
 		std::swap( m_set, other.m_set );
+		std::swap( m_end.m_next, other.m_end.m_next );
+		std::swap( m_end.m_prev, other.m_end.m_prev );
+		for( auto *set : { this, &other } ){ // note: would be trivial swap with allocated end node; unused function
+			if( set->empty() )
+				set->m_end.selfLink();
+			else
+				set->m_end.m_prev->m_next = set->m_end.m_next->m_prev = set->m_end.asNode();
+		}
 	}
 
-	iterator insert( const Value& value ){
-		init_set();
-		m_values.push_back( value );
-		const bool inserted = m_set.emplace( --end() ).second;
-		ASSERT_MESSAGE( inserted, "UnsortedSet::insert: already added" );
-		return --end();
+	iterator push_back( const Value& value ){
+		typename decltype( m_set )::iterator it;
+		if constexpr ( UniqueValues ){
+			bool inserted;
+			std::tie( it, inserted ) = m_set.emplace( value );
+			ASSERT_MESSAGE( inserted, "UnsortedSet::insert: already added" );
+		}
+		else{
+			it = m_set.emplace( value );
+		}
+		Node *newNode = &const_cast<Node&>( *it );
+		Node::link( m_end.m_prev, newNode );
+		Node::link( newNode, m_end.asNode() );
+		return iterator( newNode );
 	}
 	void erase( const Value& value ){
-		init_set();
 		const auto it = m_set.find( value );
 		ASSERT_MESSAGE( it != m_set.cend(), "UnsortedSet::erase: not found" );
-		m_values.erase( *it );
+		Node::link( it->m_prev, it->m_next );
 		m_set.erase( it );
 	}
-	const_iterator find( const Value& value ){
-		init_set();
+	const_iterator find( const Value& value ) const {
 		const auto it = m_set.find( value );
-		return it == m_set.cend()? end() : *it;
+		return ( it == m_set.cend() )? end() : const_iterator( &( *it ) );
+	}
+	Value& back(){
+		return m_end.m_prev->m_value;
+	}
+	const Value& back() const {
+		return m_end.m_prev->m_value;
 	}
 };
 
@@ -168,8 +257,8 @@ namespace std
 {
 /// \brief Swaps the values of \p self and \p other.
 /// Overloads std::swap.
-template<typename Value>
-inline void swap( UnsortedSet<Value>& self, UnsortedSet<Value>& other ){
+template<typename Value, bool UniqueValues>
+inline void swap( UnsortedSet<Value, UniqueValues>& self, UnsortedSet<Value, UniqueValues>& other ){
 	self.swap( other );
 }
 }
diff --git a/libs/entitylib.h b/libs/entitylib.h
index 0b043e3e..9f9b8f9d 100644
--- a/libs/entitylib.h
+++ b/libs/entitylib.h
@@ -304,7 +304,7 @@ public:
 /// - Provides undo support through the global undo system.
 class KeyValue final : public EntityKeyValue
 {
-	typedef UnsortedSet<KeyObserver> KeyObservers;
+	typedef UnsortedSet<KeyObserver, true> KeyObservers;
 
 	std::size_t m_refcount;
 	KeyObservers m_observers;
@@ -343,7 +343,7 @@ public:
 	}
 
 	void attach( const KeyObserver& observer ) override {
-		( *m_observers.insert ( observer ) )( c_str() );
+		( *m_observers.push_back( observer ) )( c_str() );
 	}
 	void detach( const KeyObserver& observer ) override {
 		observer( m_empty );
@@ -406,7 +406,7 @@ private:
 	typedef UnsortedMap<Key, KeyValuePtr> KeyValues;
 	KeyValues m_keyValues;
 
-	typedef UnsortedSet<Observer*> Observers;
+	typedef UnsortedSet<Observer*, true> Observers;
 	Observers m_observers;
 
 	ObservedUndoableObject<KeyValues> m_undo;
@@ -554,7 +554,7 @@ public:
 
 	void attach( Observer& observer ) override {
 		ASSERT_MESSAGE( !m_observerMutex, "observer cannot be attached during iteration" );
-		m_observers.insert( &observer );
+		m_observers.push_back( &observer );
 		for ( const auto& [ key, value ] : m_keyValues )
 		{
 			observer.insert( key.c_str(), *value );
diff --git a/libs/selectionlib.h b/libs/selectionlib.h
index 2512345c..d089437d 100644
--- a/libs/selectionlib.h
+++ b/libs/selectionlib.h
@@ -115,72 +115,3 @@ public:
 	}
 	typedef MemberCaller<SelectableInstance, void(const Selectable&), &SelectableInstance::selectedChanged> SelectedChangedCaller;
 };
-
-
-#include <list>
-#include <set>
-
-/// It's illegal to modify inserted values directly!
-template<typename Selected>
-class SelectionList
-{
-	typedef std::list<Selected*> List;
-	List m_selection;
-public:
-	typedef typename List::iterator iterator;
-	typedef typename List::const_iterator const_iterator;
-private:
-	struct Compare{
-		using is_transparent = void;
-
-		bool operator()( const const_iterator& one, const const_iterator& other ) const {
-			return *one < *other;
-		}
-		bool operator()( const Selected* va, const const_iterator& it ) const {
-			return va < *it;
-		}
-		bool operator()( const const_iterator& it, const Selected* va ) const {
-			return *it < va;
-		}
-	};
-	std::multiset<const_iterator, Compare> m_set;
-public:
-
-	SelectionList() = default;
-	SelectionList( SelectionList&& ) noexcept = delete;
-
-	iterator begin(){
-		return m_selection.begin();
-	}
-	const_iterator begin() const {
-		return m_selection.begin();
-	}
-	iterator end(){
-		return m_selection.end();
-	}
-	const_iterator end() const {
-		return m_selection.end();
-	}
-	bool empty() const {
-		return m_selection.empty();
-	}
-	std::size_t size() const {
-		return m_selection.size();
-	}
-	Selected& back(){
-		return *m_selection.back();
-	}
-	Selected& back() const {
-		return *m_selection.back();
-	}
-	void append( Selected& selected ){
-		m_selection.push_back( &selected );
-		m_set.emplace( --end() );
-	}
-	void erase( Selected& selected ){
-		const auto it = m_set.find( &selected );
-		ASSERT_MESSAGE( it != m_set.cend(), "selection-tracking error" );
-		m_selection.erase( *it );
-		m_set.erase( it );
-	}
-};
diff --git a/libs/traverselib.h b/libs/traverselib.h
index ece4d1f4..1d3afd4c 100644
--- a/libs/traverselib.h
+++ b/libs/traverselib.h
@@ -96,7 +96,7 @@ public:
 		return *this;
 	}
 };
-typedef UnsortedSet<NodeSmartReference> UnsortedNodeSet;
+typedef UnsortedSet<NodeSmartReference, true> UnsortedNodeSet;
 
 /// \brief Calls \p observer->\c insert for each node that exists only in \p other and \p observer->\c erase for each node that exists only in \p self
 inline void nodeset_diff( const UnsortedNodeSet& self, const UnsortedNodeSet& other, scene::Traversable::Observer* observer ){
@@ -182,7 +182,7 @@ public:
 
 		ASSERT_MESSAGE( m_children.find( NodeSmartReference( node ) ) == m_children.end(), "TraversableNodeSet::insert - element already exists" );
 
-		m_children.insert( NodeSmartReference( node ) );
+		m_children.push_back( NodeSmartReference( node ) );
 
 		if ( m_observer ) {
 			m_observer->insert( node );
diff --git a/radiant/brush.h b/radiant/brush.h
index 2cdaa265..d42a7379 100644
--- a/radiant/brush.h
+++ b/radiant/brush.h
@@ -2543,14 +2543,14 @@ class FaceInstance;
 
 class FaceInstanceSet
 {
-	typedef SelectionList<FaceInstance> FaceInstances;
+	typedef UnsortedSet<FaceInstance*, false> FaceInstances;
 	FaceInstances m_faceInstances;
 public:
 	void insert( FaceInstance& faceInstance ){
-		m_faceInstances.append( faceInstance );
+		m_faceInstances.push_back( &faceInstance );
 	}
 	void erase( FaceInstance& faceInstance ){
-		m_faceInstances.erase( faceInstance );
+		m_faceInstances.erase( &faceInstance );
 	}
 
 	template<typename Functor>
@@ -2565,7 +2565,7 @@ public:
 		return m_faceInstances.empty();
 	}
 	FaceInstance& last() const {
-		return m_faceInstances.back();
+		return *m_faceInstances.back();
 	}
 };
 
diff --git a/radiant/map.cpp b/radiant/map.cpp
index 53b1bab5..79013a14 100644
--- a/radiant/map.cpp
+++ b/radiant/map.cpp
@@ -519,7 +519,7 @@ public:
 	CollectAllWalker( scene::Node& root, UnsortedNodeSet& nodes ) : m_root( root ), m_nodes( nodes ){
 	}
 	bool pre( scene::Node& node ) const override {
-		m_nodes.insert( NodeSmartReference( node ) );
+		m_nodes.push_back( NodeSmartReference( node ) );
 		Node_getTraversable( m_root )->erase( node );
 		return false;
 	}
diff --git a/radiant/modelwindow.cpp b/radiant/modelwindow.cpp
index 31a2154f..774c570c 100644
--- a/radiant/modelwindow.cpp
+++ b/radiant/modelwindow.cpp
@@ -240,7 +240,7 @@ public:
 
 		ASSERT_MESSAGE( m_children.find( NodeSmartReference( node ) ) == m_children.end(), "TraversableModelNodeSet::insert - element already exists" );
 
-		m_children.insert( NodeSmartReference( node ) );
+		m_children.push_back( NodeSmartReference( node ) );
 
 		if ( m_observer ) {
 			m_observer->insert( node );
diff --git a/radiant/selection.cpp b/radiant/selection.cpp
index b7132553..34496e60 100644
--- a/radiant/selection.cpp
+++ b/radiant/selection.cpp
@@ -6946,7 +6946,7 @@ private:
 	UVManipulator m_uv_manipulator;
 	mutable TransformOriginManipulator m_transformOrigin_manipulator;
 
-	typedef SelectionList<scene::Instance> selection_t;
+	typedef UnsortedSet<scene::Instance*, false> selection_t;
 	selection_t m_selection;
 	selection_t m_component_selection;
 
@@ -7080,12 +7080,12 @@ public:
 	}
 	void onSelectedChanged( scene::Instance& instance, const Selectable& selectable ) override {
 		if ( selectable.isSelected() ) {
-			m_selection.append( instance );
+			m_selection.push_back( &instance );
 			m_count_stuff.increment( instance.path().top() );
 		}
 		else
 		{
-			m_selection.erase( instance );
+			m_selection.erase( &instance );
 			m_count_stuff.decrement( instance.path().top() );
 		}
 
@@ -7093,11 +7093,11 @@ public:
 	}
 	void onComponentSelection( scene::Instance& instance, const Selectable& selectable ) override {
 		if ( selectable.isSelected() ) {
-			m_component_selection.append( instance );
+			m_component_selection.push_back( &instance );
 		}
 		else
 		{
-			m_component_selection.erase( instance );
+			m_component_selection.erase( &instance );
 		}
 
 		ASSERT_MESSAGE( m_component_selection.size() == m_count_component.size(), "selection-tracking error" );
@@ -7108,7 +7108,7 @@ public:
 	}
 	scene::Instance& ultimateSelected() const override {
 		ASSERT_MESSAGE( m_selection.size() > 0, "no instance selected" );
-		return m_selection.back();
+		return *m_selection.back();
 	}
 	scene::Instance& penultimateSelected() const override {
 		ASSERT_MESSAGE( m_selection.size() > 1, "only one instance selected" );
@@ -7524,13 +7524,13 @@ public:
 			if ( Mode() == eComponent ) {
 				Scene_Rotate_Component_Selected( GlobalSceneGraph(), m_rotation, m_pivot2world.t().vec3() );
 
-				matrix4_assign_rotation_for_pivot( m_pivot2world, m_component_selection.back() );
+				matrix4_assign_rotation_for_pivot( m_pivot2world, *m_component_selection.back() );
 			}
 			else
 			{
 				Scene_Rotate_Selected( GlobalSceneGraph(), m_rotation, m_pivot2world.t().vec3() );
 
-				matrix4_assign_rotation_for_pivot( m_pivot2world, m_selection.back() );
+				matrix4_assign_rotation_for_pivot( m_pivot2world, *m_selection.back() );
 			}
 #ifdef SELECTIONSYSTEM_AXIAL_PIVOTS
 			matrix4_assign_rotation( m_pivot2world, matrix4_rotation_for_quaternion_quantised( m_rotation ) );
@@ -8095,20 +8095,20 @@ void RadiantSelectionSystem::ConstructPivotRotation() const {
 		break;
 	case eRotate:
 		if ( Mode() == eComponent ) {
-			matrix4_assign_rotation_for_pivot( m_pivot2world, m_component_selection.back() );
+			matrix4_assign_rotation_for_pivot( m_pivot2world, *m_component_selection.back() );
 		}
 		else
 		{
-			matrix4_assign_rotation_for_pivot( m_pivot2world, m_selection.back() );
+			matrix4_assign_rotation_for_pivot( m_pivot2world, *m_selection.back() );
 		}
 		break;
 	case eScale:
 		if ( Mode() == eComponent ) {
-			matrix4_assign_rotation_for_pivot( m_pivot2world, m_component_selection.back() );
+			matrix4_assign_rotation_for_pivot( m_pivot2world, *m_component_selection.back() );
 		}
 		else
 		{
-			matrix4_assign_rotation_for_pivot( m_pivot2world, m_selection.back() );
+			matrix4_assign_rotation_for_pivot( m_pivot2world, *m_selection.back() );
 		}
 		break;
 	default: