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

Amalgamate

FEAT 14
Activity 1 action

You create a single mighty abomination using the pieces of two expendable thralls. You destroy two of your thralls within 30 feet that are adjacent to each other, fusing them into an amalgamation. An amalgamation is a single Large thrall with a reach of 10 feet and a Speed of 25 feet. It gains a status bonus to damage rolls on its Strikes equal to your level.

Pathfinder Impossible MagicORC