I am in a largely pathfinder game with a few dnd 3.5 elements. I recently gained an ilithid template Dm fiat. He stated that I gained 4 tentacles. Do these natural attacks count as primary or secondary?
According to the Universal Monster Rules on Natural Attacks, in Pathfinder tentacles are typically secondary natural attacks, but, as with anything homebrew, you're better off asking the brewer… that is, the GM.
Keep in mind, though, that if the tentacles are the character's only natural attacks, then the rules are a bit different:
If a creature has only one natural attack, it is always made using the creature’s full base attack bonus and adds 1-1/2 times the creature’s Strength bonus on damage rolls. This increase does not apply if the creature has multiple attacks but only takes one. If a creature has only one type of attack, but has multiple attacks per round, that attack is treated as a primary attack, regardless of its type.
Emphasis mine. So if the character's only natural attacks are his face-tentacles and the character makes only attacks with his face-tentacles during his turn, then the face-tentacle attacks are, essentially, primary attacks. But were the character to gain, for example, a bite attack (or swing a sword), all the face-tentacle attacks become secondary attacks.
This means the character's attack routine could be either of the following:
If the character has no other natural weapons, the character can take a full-round action to make a full attack that is one attack with each of the four tentacles, each dealing its damage (usually 1d4 for a Medium creature's tentacle) plus ×1½ the character's Strength bonus.
If the character does have another natural attack, each tentacle attack suffers a −5 penalty on the attack roll and each tentacle attack deals its damage (again, here, usually 1d4) plus ×½ the character's Strength bonus (not ×1½!).
Alternatively, the character can take a full-round action to action to make with a manufactured weapon (like, for example, a greatsword) the character's normal attacks and its iterative attacks (if any), each attack dealing normal damage, then the character can make all of its natural attacks as secondary natural attacks, each natural attack suffering a −5 penalty on the attack roll and each natural attack dealing its damage (again, here, usually 1d4) plus ×½ the character's Strength bonus (not ×1½!). In this case, that'd be the four tentacles.
Note that any sort of Pathfinder mind flayer must be created by the GM, the illithid being "considered 'Product Identity' by Wizards of the Coast and as such is not released under its Open Game License," so, for example, the creature's absent from the Dungeons and Dragons 3.5 SRD.
This isn't a full on answer to my question, but as a martial character before the change my full attack action was always useful. So at least in practical usage, this alone should give me most of what I need.
Creatures with natural attacks and attacks made with weapons can use both as part of a full attack action (although often a creature must forgo one natural attack for each weapon clutched in that limb, be it a claw, tentacle, or slam). Such creatures attack with their weapons normally but treat all of their available natural attacks as secondary attacks during that attack, regardless of the attack’s original type- from the pathfinder srd