Sahuagin Mutants

[Chilxius]

The monster manual mentions that 0.5% of sahuagin are born with four arms, and can make four claw attacks or use 'use extra weapons'. Would that mean that it can have one primary attack and three secondary, or would you treat it has having two primary attacks?

I know most creatures with extra limbs make extra attacks as secondary (including the sahuagin), but if it takes a level adjustment for the extra arms, I feel like two primaries wouldn't be too harsh. The Marlith makes all her sword attacks at full attack bonus (though only the first can make multiple attacks).

Planning a scary boss sahuagin to throw at the party. My intention is that he wield two tridents, each in two hands. (I know the trident is one-handed, but the sea devils love their tridents).

[Necroticplague]

The monster manual mentions that 0.5% of sahuagin are born with four arms, and can make four claw attacks or use 'use extra weapons'. Would that mean that it can have one primary attack and three secondary, or would you treat it has having two primary attacks?

I know most creatures with extra limbs make extra attacks as secondary (including the sahuagin), but if it takes a level adjustment for the extra arms, I feel like two primaries wouldn't be too harsh. The Marlith makes all her sword attacks at full attack bonus (though only the first can make multiple attacks).

Planning a scary boss sahuagin to throw at the party. My intention is that he wield two tridents, each in two hands. (I know the trident is one-handed, but the sea devils love their tridents).

Primary attack? When dealing with purely manufactured weapons (i.e, not adding its claws or bite as a follow-up), there is no such thing. There's only main-hand, and off-hand. You only have one main-hand, regardless of how many off-hands you use. Using more than two weapons uses the same rules for using two weapons, just adding more off-hands. And replacing TWF with MWF as the feat needed. Penalties are gonna be rather steep for not using light weapons, even if you give it MWF.

Marilith's bonuses are a special exception due to an ability it has, though, like the Hydra, it's poorly written, and weirdly written as a special exception of it's feat.

[DrMotives]

You could try and model it based on the Diopsid, the 4-armed race from Compendium Annual. They can use a pair of 2-handed weapons, functioning as a normal race with a non-light offhand weapon. They also can use an oversized weapon by bracing it with a secondary arm. Thus, a pair of oversized tridents, each one with 1.5x str bonus and normal TWF penalties for a non-light offhand weapon would apply. Sahugin also can, per fluff, keep growing into kaiju-like sizes, so a 400 year old 4-arm mutant sahugin king might be Large, and wield a pair of Huge tridents. If he makes it to a thousand years old, he'd probably be Huge and could swing Gargantuan tridents. They never die of old age after all, they just keep getting bigger but also starting sleeping for years in hiding, coming out infrequently as more & more legendary creatures.

[InterstellarPro]

In my games, I house rule using two two-handed weapons as the first one gets 1.5x str while the second gets .75 str (rather than .5 str). Basically, you halve it, then halve it again. So, the attacks would be:

Str 12: 1d8+1, 1d8
Str 14: 1d8+3, 1d8+1
Str 16: 1d8+4, 1d8+1
Str 18: 1d8+6, 1d8+3
Str 20: 1d8+7, 1d8+3
Str 22: 1d8+9, 1d8+4
Str 24: 1d8+10, 1d8+4
Str 26: 1d8+12, 1d8+6

This is only very slightly better damage than a straight off-hand attack, but makes me feel like the mutant is getting some additional advantage for having extra arms and knowing how to use them.