Monster with spears for legs

[Yora]

I want to make a custom monster that is pretty much a giant crab with extremely long legs that it uses to stab its prey. I think this deserves something a bit more elaborate than just a melee weapon attack that deals piercing damage. Are the any creature in the MM or Volo with interesting abilities I could use? Like pinning a target to the floor or something like that?

[some guy]

The Lonely (sorrowsworn) in Mordenkainen's has a harpoon arm that grapples a target on hit (with an escape DC), it can only grapple as much targets as it has harpoon arms. That could be copied.

Pinning someone could be an attack with a Dex save or be Restrained. While pinning the crab monster has a move of 0 ft.

[nickl_2000]

Pinning someone could be an attack with a Dex save or be Restrained. While pinning the crab monster has a move of 0 ft.

I agree with the Dex save, but I think the move speed of 0 will depend on how many legs it has and the size. A large creature with 8 legs could easily move around while it has someone pinned with one leg.

I would have it do some damage every turn to a pinned person, and the crab can't attack anyone else with that attack (after all, it is hard to attack when you have a humanoid stick on your leg).

[NRSASD]

I'd use the mechanics of the "pounce" ability, that the saber tooth tiger gets, and give it an extra leg attack instead of a free bite. As far as damage goes, it depends on what level you want the monster to be, but anywhere from 1d8 to 4d8 feels about right to me.

From my own experience running large groups, singular monsters are not very strong; regardless of their statline. Once it has pinned someone, I'd have it emit a cloud of phermomes/toxins/etc. to keep the other PCs away while it eats their friend. Take a look at the demon Vrock for an idea of how to implement that.

[Yora]

Looking at the conditions again, another option might be to let the monster give up one of its attacks to keep the target restrained, allowing it to keep atacking with its other legs. Though logically, the target would also be prone, which gets a bit confusing whether attackers have advantage or disadvantage on attacks against it.

Actually, it could simply be identical to the constrict ability. The marilith has even one that automatically deals damage every round: "If the target is Medium or smaller, it is grappled (escape DC 19). Until this grapple ends, the target is restrained, the marilith can automatically hit the target with its tail, and the marilith can’t make tail attacks against other targets."

Even if the legs are described as being like spears, a nonlethal hit obviously couldn't mean being impaled through the chest. It would be more like partially penetrating the armor, and each round the monster keeps pressing down further, stabbing deeper into the body and also crushing the chest.

[tchntm43]

Neogi are kind of like that. Their front legs are like big spears with sawblade edges. They're pretty weak, overall, though.

[Millstone85]

Neogi are kind of like that. Their front legs are like big spears with sawblade edges. They're pretty weak, overall, though.

A similar-looking monster is the kruthik from MToF.

[TripleD]

Could the legs be detachable? Sort of like a gecko’s tail? With eight legs it could probably afford to lose four before mobility becomes an issue.

As for what to do to the pinned creature, have you ever heard of the “Yeti Crab”? Technically they aren’t a true crab, but they are a crustacean that grows bacteria and algae on its claws to feed on later.

Maybe your creature could have a similar feature. It’s hunting method is to pin a creature, then release a swarm of vermin living in its own hairs to devour the creature with the intention of later coming back and eating the bloated and expanded swarm.

Gameplay wise this could be a swarm that is “summoned” on the same space when a creature is pinned. If you want to be extra sadistic you could make the swarm gain HP as it deals damage to the creature to reflect it “feasting” on the adventurer.

[MrStabby]

Massive AC and pinning the PCs does sound like it could force some tough decisions. Dex save spells would be an attractive way of doing damage but they could be collaterally damaging the party.

I would make it dex to dodge then Str to break free. This way it feels less like it is going to be persecuting a particular party member.

[Yora]

I thought about giving it really long legs. So I am giving it damage resistance against all attacks that have a reach of 5 or 10 feet. Hitting the legs won't be doing much damage.

I also think that Mr. Stabby would make a great informal name for it.

[NRSASD]

While mechanically speaking it's not terribly interesting, you should definitely look at the 2nd edition sword spider. It's literally the creature you're describing