pf2e.fyi
From Pathfinder Impossible Magic, which isn't enabled.

Dutiful Retaliation

REACTION
Activity reaction

Trigger An enemy within 15 feet of you hits you with a Strike and deals damage to you
Requirements Your eidolon is within 15 feet of you

Effect Your eidolon instinctively flashes with ectoplasmic energy, allowing them to strike back against an enemy who dares to harm you. Your eidolon makes a melee unarmed Strike against the triggering enemy, even if that enemy isn't within your eidolon's reach.
Pathfinder Impossible MagicORC