Key
Opaque identifier for game-facing registries (items, blocks, materials, models, prefabs, etc.).
Design note
This is intentionally not an enum: registries may be huge and may evolve.
This is intentionally not tied to any host API: it can map to strings, hashes, resource locations, etc.
Java-friendly: this is a normal class (not a Kotlin value class).
Example
IDs can be plain strings such as Cloth_Block_Wool_Blue (as seen in Hytale UI/tooling). KTale preserves the string verbatim; it does not enforce casing or separators.