It's a server-side Fabric addon for Cobblemon (1.21.1) that makes wild Pokemon feel alive by giving them aggressive and timid behaviors.

Core Behaviors

Aggressive Pokemon

Actively hunt and attack players within range (default 16 blocks)
Use their actual moveset to deal damage — move power, Pokemon stats, and accuracy all factor in
Apply secondary effects from moves: burns set you on fire, paralysis slows you, poison applies the poison effect, etc.
Spawn type-appropriate particles on hit (e.g., fire impact for Fire moves)
Higher levels (1–5) = more damage, faster attacks, shorter cooldowns

Timid Pokemon

Flee from players when detected within range (default 10 blocks)
Higher levels = faster flee speed

Natural Spawning

Wild Pokemon have a random chance to spawn with a behavior (5% aggressive, 10% timid by default)
Higher levels are exponentially rarer
Only in whitelisted dimensions (overworld by default)

Player Interaction

Oran Berry (right-click): calms aggressive Pokemon in an 8-block radius
Pecha Berry (right-click): soothes timid Pokemon nearby
Works with /pokespawn — e.g., /pokespawn charizard aggressive=3

Key Design Principles

Additive AI: injects goals via GoalSelector without overwriting Cobblemon's existing AI
Never targets owned Pokemon or Pokemon in battle
Fully configurable via config/cobblemonbehaviours.json (damage, ranges, spawn rates, items, cooldowns, etc.)
Server-side only — no client mod needed

In short: it turns wild Pokemon from passive decorations into dynamic encounters — some will chase you down and fight using real moves, others will run away when you approach.