diff --git a/internal/packets/login/BadLanguageFilter.xml b/internal/packets/login/BadLanguageFilter.xml
index 660c7e6..0163c29 100644
--- a/internal/packets/login/BadLanguageFilter.xml
+++ b/internal/packets/login/BadLanguageFilter.xml
@@ -2,9 +2,7 @@
 	<version number="1">
 		<i16 name="num_words" oversized="255">
 		<array name="words_array" count="var:num_words">
-			<substruct>
-				<str16 name="word">
-			</substruct>
+			<str16 name="word">
 		</array>
 	</version>
 </packet>
\ No newline at end of file
diff --git a/internal/packets/parser/parser.go b/internal/packets/parser/parser.go
index 3c0efde..ca4ab1a 100644
--- a/internal/packets/parser/parser.go
+++ b/internal/packets/parser/parser.go
@@ -8,7 +8,6 @@ import (
 	"sync"
 )
 
-// Object pools for reducing allocations
 var (
 	fieldOrderPool = sync.Pool{
 		New: func() any {
@@ -29,7 +28,6 @@ var (
 	}
 )
 
-// String builder for efficient concatenation
 type stringBuilder struct {
 	buf []byte
 }
@@ -52,6 +50,7 @@ type Parser struct {
 	current    *Token
 	input      string
 	substructs map[string]*PacketDef
+	templates  map[string]*PacketDef
 	tagStack   []string
 	fieldNames []string
 }
@@ -68,7 +67,7 @@ var typeMap = map[string]common.EQ2DataType{
 	"si64":   common.TypeSInt64,
 	"f32":    common.TypeFloat,
 	"f64":    common.TypeDouble,
-	"double": common.TypeDouble, // XML compatibility
+	"double": common.TypeDouble,
 	"str8":   common.TypeString8,
 	"str16":  common.TypeString16,
 	"str32":  common.TypeString32,
@@ -84,6 +83,7 @@ func NewParser(input string) *Parser {
 		lexer:      NewLexer(input),
 		input:      input,
 		substructs: make(map[string]*PacketDef),
+		templates:  make(map[string]*PacketDef),
 		tagStack:   make([]string, 0, 16),
 		fieldNames: make([]string, 0, 8),
 	}
@@ -285,14 +285,6 @@ func combineConditions(cond1, cond2 string) string {
 	return string(buf)
 }
 
-// Creates packet definition with estimated capacity
-func NewPacketDef(estimatedFields int) *PacketDef {
-	return &PacketDef{
-		Fields: make(map[string]FieldDesc, estimatedFields),
-		Orders: make(map[uint32][]string, 4),
-	}
-}
-
 // Parses the entire PML document
 func (p *Parser) Parse() (map[string]*PacketDef, error) {
 	packets := make(map[string]*PacketDef)
@@ -322,6 +314,16 @@ func (p *Parser) Parse() (map[string]*PacketDef, error) {
 				if name != "" {
 					p.substructs[name] = substruct
 				}
+			case "template":
+				name := p.current.Attributes["name"]
+				if name != "" {
+					err := p.parseTemplateDefinition(name)
+					if err != nil {
+						return nil, err
+					}
+				} else {
+					p.advance()
+				}
 			default:
 				p.advance()
 			}
@@ -468,6 +470,11 @@ func (p *Parser) parseElements(packetDef *PacketDef, fieldOrder *[]string, prefi
 				if err != nil {
 					return err
 				}
+			case "template":
+				err := p.parseTemplate(packetDef, fieldOrder, prefix)
+				if err != nil {
+					return err
+				}
 			default:
 				err := p.parseField(packetDef, fieldOrder, prefix)
 				if err != nil {
@@ -483,6 +490,90 @@ func (p *Parser) parseElements(packetDef *PacketDef, fieldOrder *[]string, prefi
 	return nil
 }
 
+// Handles template definition and usage
+func (p *Parser) parseTemplate(packetDef *PacketDef, fieldOrder *[]string, prefix string) error {
+	attrs := p.current.Attributes
+
+	// Template definition: <template name="foo">
+	if templateName := attrs["name"]; templateName != "" {
+		return p.parseTemplateDefinition(templateName)
+	}
+
+	// Template usage: <template use="foo">
+	if templateUse := attrs["use"]; templateUse != "" {
+		return p.parseTemplateUsage(packetDef, fieldOrder, prefix, templateUse)
+	}
+
+	// No name or use attribute - skip
+	p.advance()
+	return nil
+}
+
+// Parses template definition and stores it
+func (p *Parser) parseTemplateDefinition(templateName string) error {
+	templateDef := NewPacketDef(16)
+	fieldOrder := fieldOrderPool.Get().(*[]string)
+	*fieldOrder = (*fieldOrder)[:0]
+	defer fieldOrderPool.Put(fieldOrder)
+
+	if p.current.Type == TokenSelfCloseTag {
+		p.advance()
+		templateDef.Orders[1] = make([]string, len(*fieldOrder))
+		copy(templateDef.Orders[1], *fieldOrder)
+		p.templates[templateName] = templateDef
+		return nil
+	}
+
+	p.pushTag("template")
+	p.advance()
+
+	err := p.parseElements(templateDef, fieldOrder, "")
+	if err != nil {
+		return err
+	}
+
+	if p.current.Type == TokenCloseTag && p.current.Tag(p.input) == "template" {
+		if err := p.popTag("template"); err != nil {
+			return err
+		}
+		p.advance()
+	} else {
+		return fmt.Errorf("expected closing tag for template at line %d", p.current.Line)
+	}
+
+	templateDef.Orders[1] = make([]string, len(*fieldOrder))
+	copy(templateDef.Orders[1], *fieldOrder)
+	p.templates[templateName] = templateDef
+	return nil
+}
+
+// Injects template fields into current parsing context
+func (p *Parser) parseTemplateUsage(packetDef *PacketDef, fieldOrder *[]string, prefix string, templateName string) error {
+	template, exists := p.templates[templateName]
+	if !exists {
+		return fmt.Errorf("undefined template '%s' at line %d", templateName, p.current.Line)
+	}
+
+	// Inject all template fields into current packet
+	if templateOrder, exists := template.Orders[1]; exists {
+		for _, fieldName := range templateOrder {
+			if fieldDesc, exists := template.Fields[fieldName]; exists {
+				// Apply prefix if provided
+				fullName := fieldName
+				if prefix != "" {
+					fullName = buildFieldName(prefix, fieldName)
+				}
+
+				packetDef.Fields[fullName] = fieldDesc
+				*fieldOrder = append(*fieldOrder, fullName)
+			}
+		}
+	}
+
+	p.advance()
+	return nil
+}
+
 // Handles group elements
 func (p *Parser) parseGroup(packetDef *PacketDef, fieldOrder *[]string, prefix string) error {
 	attrs := p.current.Attributes
@@ -520,7 +611,7 @@ func (p *Parser) parseGroup(packetDef *PacketDef, fieldOrder *[]string, prefix s
 	return nil
 }
 
-// Handles array elements - FIXED: Remove redundant substruct wrapper
+// Handles array elements
 func (p *Parser) parseArray(packetDef *PacketDef, fieldOrder *[]string, prefix string) error {
 	attrs := p.current.Attributes
 
diff --git a/internal/packets/parser/parser_test.go b/internal/packets/parser/parser_test.go
index e1afb25..ec3ecfe 100644
--- a/internal/packets/parser/parser_test.go
+++ b/internal/packets/parser/parser_test.go
@@ -720,6 +720,102 @@ func TestErrorHandling(t *testing.T) {
 	}
 }
 
+func TestTemplateDefinitionAndUsage(t *testing.T) {
+	pml := `<!-- Define reusable templates -->
+	<template name="position">
+		<f32 name="x,y,z">
+		<f32 name="heading">
+	</template>
+	
+	<template name="appearance">
+		<color name="skin_color,hair_color,eye_color">
+		<str16 name="face_file,hair_file">
+	</template>
+
+	<!-- Use templates in packet -->
+	<packet name="PlayerUpdate">
+		<version number="1">
+			<i32 name="player_id">
+			<template use="position">
+			<i8 name="level">
+			<template use="appearance">
+			<str16 name="guild_name" if="flag:has_guild">
+		</version>
+	</packet>
+	
+	<!-- Test template with group prefix -->
+	<packet name="GroupedTemplate">
+		<version number="1">
+			<i32 name="entity_id">
+			<group name="current">
+				<template use="position">
+			</group>
+			<group name="target">
+				<template use="position">
+			</group>
+		</version>
+	</packet>`
+
+	packets, err := Parse(pml)
+	if err != nil {
+		t.Fatalf("Parse failed: %v", err)
+	}
+
+	// Test basic template injection
+	playerPacket := packets["PlayerUpdate"]
+	if playerPacket == nil {
+		t.Fatal("PlayerUpdate packet not found")
+	}
+
+	// Check that template fields were injected
+	expectedFields := []string{"player_id", "x", "y", "z", "heading", "level", "skin_color", "hair_color", "eye_color", "face_file", "hair_file", "guild_name"}
+	if len(playerPacket.Fields) != len(expectedFields) {
+		t.Errorf("Expected %d fields, got %d", len(expectedFields), len(playerPacket.Fields))
+	}
+
+	// Verify specific template fields exist with correct types
+	if playerPacket.Fields["x"].Type != common.TypeFloat {
+		t.Error("x should be TypeFloat from position template")
+	}
+	if playerPacket.Fields["heading"].Type != common.TypeFloat {
+		t.Error("heading should be TypeFloat from position template")
+	}
+	if playerPacket.Fields["skin_color"].Type != common.TypeColor {
+		t.Error("skin_color should be TypeColor from appearance template")
+	}
+	if playerPacket.Fields["face_file"].Type != common.TypeString16 {
+		t.Error("face_file should be TypeString16 from appearance template")
+	}
+
+	// Check field ordering preserves template injection points
+	order := playerPacket.Orders[1]
+	expectedOrder := []string{"player_id", "x", "y", "z", "heading", "level", "skin_color", "hair_color", "eye_color", "face_file", "hair_file", "guild_name"}
+	if !equalSlices(order, expectedOrder) {
+		t.Errorf("Expected order %v, got %v", expectedOrder, order)
+	}
+
+	// Test template with group prefixes
+	groupedPacket := packets["GroupedTemplate"]
+	if groupedPacket == nil {
+		t.Fatal("GroupedTemplate packet not found")
+	}
+
+	// Check prefixed fields from templates
+	if groupedPacket.Fields["current_x"].Type != common.TypeFloat {
+		t.Error("current_x should exist from prefixed template")
+	}
+	if groupedPacket.Fields["target_heading"].Type != common.TypeFloat {
+		t.Error("target_heading should exist from prefixed template")
+	}
+
+	// Verify grouped template field order
+	groupedOrder := groupedPacket.Orders[1]
+	expectedGroupedOrder := []string{"entity_id", "current_x", "current_y", "current_z", "current_heading", "target_x", "target_y", "target_z", "target_heading"}
+	if !equalSlices(groupedOrder, expectedGroupedOrder) {
+		t.Errorf("Expected grouped order %v, got %v", expectedGroupedOrder, groupedOrder)
+	}
+}
+
 func BenchmarkSimplePacket(b *testing.B) {
 	pml := `<packet name="Simple">
 		<version number="1">
@@ -738,27 +834,53 @@ func BenchmarkSimplePacket(b *testing.B) {
 	}
 }
 
-func BenchmarkComplexPacketWithNewFeatures(b *testing.B) {
-	pml := `<packet name="Complex">
-		<version number="562">
-			<i32 name="player_id,account_id">
-			<str16 name="player_name">
-			<color name="skin_color,hair_color,eye_color">
-			<str16 name="guild_name" if="flag:has_guild">
-			<i32 name="guild_id" if="flag:has_guild">
-			<i8 name="equipment_count">
-			<array name="equipment" count="var:equipment_count" max_size="50">
-				<i16 name="slot_id,item_type">
-				<color name="primary_color,secondary_color">
-				<i8 name="enhancement_level" if="item_type!=0">
-				<i32 name="stat_value" type2="f32" type2_if="item_type==6" oversized="255">
-			</array>
-			<i8 name="stat_count">
-			<array name="stats" count="var:stat_count" optional="true">
-				<i8 name="stat_type">
-				<i32 name="base_value">
-				<i32 name="modified_value" if="stat_type>=1&stat_type<=5">
-				<f64 name="percentage" if="stat_type==6">
+func BenchmarkMediumPacket(b *testing.B) {
+	pml := `<packet name="Medium">
+		<version number="1">
+			<i32 name="id,account_id,session_id">
+			<str16 name="name,guild_name">
+			<i8 name="level,race,class">
+			<f32 name="x,y,z,heading">
+			<color name="skin_color,hair_color">
+		</version>
+	</packet>`
+
+	for b.Loop() {
+		_, err := Parse(pml)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkLargePacket(b *testing.B) {
+	pml := `<packet name="Large">
+		<version number="1">
+			<i32 name="a1,a2,a3,a4,a5,a6,a7,a8,a9,a10">
+			<str16 name="s1,s2,s3,s4,s5">
+			<f32 name="f1,f2,f3,f4,f5,f6,f7,f8">
+			<color name="c1,c2,c3,c4">
+			<i8 name="b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12">
+		</version>
+	</packet>`
+
+	for b.Loop() {
+		_, err := Parse(pml)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkArrayPacket(b *testing.B) {
+	pml := `<packet name="ArrayPacket">
+		<version number="1">
+			<i8 name="count">
+			<array name="items" count="var:count">
+				<i32 name="id">
+				<str16 name="name">
+				<color name="color">
+				<f32 name="x,y,z">
 			</array>
 		</version>
 	</packet>`
@@ -771,6 +893,33 @@ func BenchmarkComplexPacketWithNewFeatures(b *testing.B) {
 	}
 }
 
+func BenchmarkMultiVersionPacket(b *testing.B) {
+	pml := `<packet name="MultiVersion">
+		<version number="1">
+			<i32 name="id">
+			<str16 name="name">
+		</version>
+		<version number="100">
+			<i32 name="id">
+			<str16 name="name">
+			<i8 name="level">
+		</version>
+		<version number="500">
+			<i32 name="id">
+			<str16 name="name">
+			<i8 name="level">
+			<color name="color">
+		</version>
+	</packet>`
+
+	for b.Loop() {
+		_, err := Parse(pml)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
 // Helper function to compare slices
 func equalSlices(a, b []string) bool {
 	if len(a) != len(b) {
diff --git a/internal/packets/parser/structs.go b/internal/packets/parser/structs.go
index 356db6c..9251f4d 100644
--- a/internal/packets/parser/structs.go
+++ b/internal/packets/parser/structs.go
@@ -8,6 +8,14 @@ type PacketDef struct {
 	Orders map[uint32][]string  // Field order by version number
 }
 
+// Creates packet definition with estimated capacity
+func NewPacketDef(estimatedFields int) *PacketDef {
+	return &PacketDef{
+		Fields: make(map[string]FieldDesc, estimatedFields),
+		Orders: make(map[uint32][]string, 4),
+	}
+}
+
 func (def *PacketDef) Parse(data []byte, version uint32, flags uint64) (map[string]any, error) {
 	ctx := NewContext(data, version, flags)
 	return def.parseStruct(ctx)