A simple question, but fairly involved when one thinks of it.
The half-fiend template adds 2 claw attacks to the base creature.
Does it still add them if the base creature (assume it's monstrous) does not possess arms/equivalent limbs to tack them onto?
What base-creature are we talking about?
Er... does it matter, in this case?
Here, I'll name some candidates from the Bestiary - Aboleth, Behir, Kraken, Naga, Remorhaz. Could look up more.
Well the Behir for one has legs, so I'd say 2 of them grow claws and he can attack with that. I think the Remorhaz too.
The others are a bit more tricky, but consider that a half-fiend is not a normal specimen of that race. Having it grow some sort of tentacle claws or something it can use in addition to its normal tentacles, either at the end of 2 already existing ones or by growing a complete new pair of limbs, whichever seems to fit better, is not really that far out there.