Multiattack works the same as 3.5 in that it lessens the secondary attack penalty from -5 to -2.
What Pathfinder did was changed which attacks were considered primary and secondary. Now a monster can have more than one 'primary' attack.
Its all covered on Pg 302 of the Bestiary.
I searched for answers, but only found old archived material.
How does multiattack work in Pathfinder? I notice some creatures in the Bestiary (an Owlbear, for example) has 3 attacks, but suffers no penalty on any of them (+8 on both claws and bite - many other examples exist: chimera, bone devils, leopards, you name it) despite not having multiattack, while other creatures like an Otyugh (2 tentacles and a bite) have the typical -5 penalty for a secondary attack, and others like a unicorn have multiattack and have the -2 penalty.
Is there a simple rule for determining whether all a creature's attacks should have the same bonus (as a bone devil has for claws, bite, and sting, or a chimera has for bite, bite, gore, claw, claw) or for different bonuses (as a cornugon has, where bite and claws are one bonus, but the tail has a -2 penalty?)
I am converting creatures and simply unsure sometimes as to whether I should bother to use a feat on multiattack if the creature would already have full BAB attacking on all its various attack forms.
from what I read on some other posts, multiattack effectively does nothing to a creature that only has multiple primary attacks (like a bite and 2 claws) since they do not meet the requirement of "only having one attack" nor the requirement of "having a secondary attack."
Zag is correct.