1. Base and donor
Fusion takes two fighters: a base (the chicken whose role you keep) and a donor (the one supplying the trait or stats). A common bird can be the base if the donor carries the special ability you want.
2. Lock the trait, not the vibe
The fuse screen lets you lock a visible trait from the donor. Pick a trait that actually helps: a stronger attack role, a good laying trait or a rare ability. Locking a flashy-but-useless trait wastes the fusion.
3. Read the live cost
Fusion costs scale as your roster grows. The display updates with the current price — check it before confirming. If the cost is too high, farm more or fuse a cheaper pair. Budget it properly with the resource calculator.
4. The Thunder Egg route
A popular path is using Thunder Egg fighters as donors for their elemental traits. It's the most documented fusion route in the community and a reliable way to upgrade a mid-tier base.
Result-check rule.
After fusing, compare the output fighter to the tier list. If the result isn't better than your current best, the fusion wasn't an upgrade.
Keep fusing smart
Fusion pairs best with a big common-roster from hatched eggs. Build the roster first, then fuse the duplicates upward. For which fusion-carried specials are worth chasing, see the best skills ranking.