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Documentation Index

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Mythical Forms are client-side player model replacements tied to a player’s pathway progression. When the server sends a coi-client:mythical plugin message payload, COI Client looks up the matching MythicalCreatureForm implementation, stores it in MythicalFormManager keyed by the player’s UUID, and from that point on the PlayerRendererMixin cancels vanilla player rendering and submits custom procedural geometry instead. All animation, coloring, and geometry calculations happen entirely on the client — the server only needs to send the pathway name, tier, and action.

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Registered Forms

The following 20 forms are registered at startup. Each corresponds to a distinct pathway in the Circle of Imagination lore.
Form NamePathway Description
FoolCluster of translucent, layered Spirit Body Thread maggots
DoorMass of glowing cosmic bubbles hiding layered eyes inside
ErrorInterconnected stereoscopic clock-segment Worms of Time
TowerBlinding pure light swirling with infinite knowledge symbols
VisionaryColossal golden dragon whose eyes contain entire illusory worlds
SunFormless blazing fireball of single-cell abstract-symbol organisms
TyrantTowering lightning-wreathed silhouette with deep-blue scaled tentacles
HangedMassive shadow bound in grotesque chains and an upside-down cross
DarknessPitch-black hound-spider hybrid radiating eternal silence and dreams
DeathFloating feathered bone-serpent with pale-blue soul-fire eyes
GiantColossal armored giant glowing with the dim light of impending sunset
PriestTowering being of raging crimson flames shaped like an armored warlord
DemonessTerrifying fog-and-spider-thread female figure hiding plague and disease
ParagonAbstract bronze-gear and steam-piston structure processing industrial blueprints
HermitHooded humanoid of purple information streams and blinking forbidden eyes
FortuneMulti-layered rotating wheel engraved with divination cards and fate threads
ChainedDistorted humanoid in rust-iron chains straining to burst into beast form
AbyssEver-changing mass of black flesh, mouths, limbs, and maddening tentacles
JusticiarGolden balance scale with an armored judge silhouette enforcing absolute order
EmperorShadow-imperial figure in a spiked crown warping laws and physical rules

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How Transformations Work

1

Server sends MythicalFormPayload

The server dispatches a coi-client:mythical plugin message containing the target player’s UUID and a params string formatted as <pathwayName>:<tier>:<action> (e.g., fool:5:start).
2

MythicalFormManager stores the active form

MythicalFormManager.handlePacket() parses the params string. If the action is "start" (or any value other than "stop"), it stores the lowercase pathway name in a ConcurrentHashMap keyed by the player’s UUID string. If the action is "stop", the entry is removed and vanilla rendering resumes.
3

PlayerRendererMixin intercepts the render pipeline

On every render frame, PlayerRendererMixin checks whether the entity being rendered is a player with an active form via MythicalFormManager.isTransformed(). If a form is active, the mixin takes over — vanilla player model submission is cancelled with ci.cancel().
4

Custom geometry is submitted via SubmitNodeCollector

The mixin submits custom geometry through collector.order(0).submitCustomGeometry(...), using the translucent white texture coi-client:textures/entity/white.png. Per-vertex RGBA values in each form’s render() call define all coloring and transparency.
5

Player nameplate is preserved

Before cancelling vanilla rendering, the mixin explicitly calls callSubmitNameDisplay so the player’s name tag continues to render above the custom form at the correct position.

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Rendering Pipeline

Forms use Minecraft 1.21.2+‘s deferred, state-based rendering system. Instead of an immediate render(...) call, geometry is queued through a SubmitNodeCollector and flushed later in the frame. Key technical details:
  • Gaze alignment — the PoseStack is pre-rotated around the Y-axis by (180° − state.bodyRot) before geometry submission, so the form always faces the direction the player’s camera is looking.
  • Translucent vertex data — all geometry is submitted under the entityTranslucent render type with the solid-white base texture. Color and alpha are encoded per-vertex in each form’s render(AvatarRenderState, PoseStack.Pose, VertexConsumer) implementation.
  • Draw helpers — MythicalCreatureForm provides two default interface methods: drawBox(...) for axis-aligned cuboids and addVertex(...) for raw vertex submission, both forwarding directly to the VertexConsumer.
  • Procedural animation — forms drive animation from state.ageInTicks, feeding that value into sine/cosine expressions to produce oscillation, rotation, and pulsing without any external animation state.

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Form Name Normalization

MythicalFormManager.register() stores each form under five key variants simultaneously to make lookups resilient to inconsistent server-side formatting: 
// All five variants are stored for every registered form
REGISTERED_FORMS.put(name,                          form); // "tower"
REGISTERED_FORMS.put(name.replace(" ", ""),         form); // "tower" (no-op for single-word names)
REGISTERED_FORMS.put(name.replace("_", ""),         form); // "tower" (strips underscores if present)
REGISTERED_FORMS.put(name.replace(" ", "_"),        form); // "tower" (no-op for single-word names)
REGISTERED_FORMS.put(name.replace("_", " "),        form); // "tower" (converts underscores to spaces)
All keys are lowercased before storage. This means the server can send Tower, tower, TOWER, or underscore-separated variants and the correct form will still be found.
Adding new forms requires modifying the COI Client source — there is no runtime registration API. See /extending/custom-forms for a step-by-step guide to implementing and registering a new MythicalCreatureForm.
Want to create a fully custom creature form with your own geometry, colors, and procedural animation? Head over to /extending/custom-forms for the complete developer guide, including boilerplate code and aesthetic best practices.

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