Grimlock

A grimlock ally is a guide. The party needs to cross the Underdark, and a grimlock clan owes a favor to a deep-gnome NPC, or a single grimlock has been exiled from its tribe and attached itself to the cleric who fed it. Run the grimlock as a near-mute companion who communicates by tapping cudgels and pointing. It has no languages and a Charisma of 6, so do not try to give it a personality through dialogue. Its personality is in the way it moves: silent, confident in the dark, hunched in the light.

In combat, the grimlock is a CR 1/4 melee piece. AC 11 and 11 HP mean it dies fast to anything serious, so use it as a flanker against a single enemy or as a scout that triggers an ambush and falls back. One Bone Cudgel attack at +5 for 6 average bludgeoning plus 2 psychic is its whole offense. It does not flank intelligently, but it does follow simple commands: bite this, hold this rope, watch that door.

Out of combat, the value is Blindsight 30 ft. and a cave-native's instincts. The grimlock walks point in the dark, smells the difference between a mineral seam and an iron door, and panics audibly when something Large is breathing in the next chamber. Stealth +5 and Athletics +5 make it a usable scout for short forays. The catch: bring it into sunlight and it shrinks, covers its face, and stops being useful until you get back underground. The party's choice to keep it on the surface or send it home is a real character beat for whoever befriended it.

Have the grimlock leave a small carved bone in a PC's pack the morning it leaves. They will never know what the symbol means.

A grimlock is a blind cave-dweller that hunts in packs through total darkness. AC 11 and 11 HP make a single one a one-round speed bump, but Blindsight 30 ft. means light, invisibility, and darkness spells do nothing against them. The party's wizard with Darkness on a coin is the first one ambushed, because the grimlock cannot tell the difference. Run them in a pack of six to ten in a tight tunnel and the encounter changes shape entirely.

Open by killing the lights. The party rounds a corner and someone kicks their torch into a pool, or a grimlock from a side tunnel slings a wet rag over the lantern. Now the party is in disadvantage on attacks (heavily obscured) and the grimlocks are not. Each grimlock attacks with Bone Cudgel at +5 for 6 average bludgeoning plus 2 psychic. The psychic is the texture: the cudgels are carved with screaming faces and they hum when they hit. Have the cleric flinch when the first one lands.

Positioning is the whole fight. Grimlocks have a 30 ft. climb speed, so they come down walls and from ceilings, not just from in front. Stealth +5 means a passive Perception 12 party still gets surprised. Use the climb to put two grimlocks behind the party while the rest engage from the front, then collapse the line. Athletics +5 lets one grab a fallen torch and run it 30 ft. into the next chamber to lure the party deeper. They are tactical because they have to be: at 11 HP each, any single grimlock dies to a longsword crit, so the pack wins through numbers and terrain or it does not win at all.

When the pack is down to two or three, they break and scatter into the cave system. They are not loyal. They will be back tomorrow with friends, and they remember which PC threw the fire spell. Have one of the survivors leave a scratched cudgel-mark on the party's camp wall during the night. The party should know they are being watched.