Action: Seething Frenzy

Your eidolon's fury boils over into a reckless, out-of-control frenzy. While frenzied, your eidolon is affected by Boost Eidolon and gains temporary Hit Points equal to your level, but takes a –1 penalty to AC. Your eidolon can't voluntarily end the frenzy or start another frenzy while in the frenzy. The frenzy and the accompanying temporary Hit Points last for 1 minute or until your eidolon is no longer manifested, whichever comes first, after which they can't start another frenzy for 1 minute.

When your eidolon makes a Furious Strike while in a Seething Frenzy, the status bonus from boost eidolon is 3 per damage die. The extra damage die from Furious Strike still doesn't count toward boost eidolon's bonus, as normal for weapon dice added by abilities.