Item bias tilts the shop toward packs you already own items from. When you're hunting a specific item, buying a cheap item from the same pack makes the one you want more likely to appear.
How it works
- Each item you own from a pack adds 1 to that pack's bias.
- A triple (a 3 star fused item) counts as 3.
- Bias is capped at 4 per pack, so there's no benefit to stacking past that point.
In practice: when you need a key item, grab the cheapest filler from its pack to tilt future shops your way, then sell the filler if you don't end up needing it.