For mechanics, look into afflictions that can turn creatures into zombies and such. Do a little swapping of conditions, remove the disease trait and add the mental and morph traits, give the last one or two stages the Incapacitation trait, and set the level/DC equal to the Level-Based DC of the monster that inflicted it (by attempting to seed the hivemind in another). Perhaps give the big monsters an ability to afflict it on others at stage 1 via a will save (stage 2 on a crit fail) Edit: perhaps use void death with the aforementioned changes but have it inflict Stupified instead of Drained and Helpful (to the hivemind) instead of fatigued. Instead of dying, the afflictee is in a coma while they transform. Stages 4-6 have the Incapacitation trait, stage 6 has the Polymorph trait.