Furious Strike

Your eidolon makes a melee Strike. This counts as two attacks when calculating your multiple attack penalty. If this Strike hits, your eidolon deals an extra die of weapon damage and gains a +1 circumstance bonus to the damage roll.

If you're at least 10th level, increase this to two extra dice with a +2 circumstance bonus, and if you're at least 18th level, increase it to three extra dice with a +3 circumstance bonus.