Focus Crystal

The Focus Crystal is an item introduced in Risk of Rain 2.

Hitting an enemy within 13 units of the character will apply a 1.15 (+0.15 per stack) multiplier to the damage dealt.

The 13 units are measured as a sphere around the character.

This item is extremely powerful to stack as Commando, Mercenary, Loader, and MUL-T since most of their attacks will fall within the 13 unit range of the Focus Crystal, meaning that it is essentially a consistent damage buff. Other characters will be frequently attacking from far outside of the activation range.