Clay Golem

A clay golem ally means the party has either inherited a relic-guardian or struck a bargain with the priesthood that built it. Constructs of this caliber are temple property, and the party gets to use it for one specific task before it returns to its post. Frame the loan up front: the high priest hands them a command word, names the limit (one mission, three days, one specific intruder), and warns about Berserk.

In play, the golem follows simple verbal orders in Common (or one other language the priesthood programmed in). Stand here. Strike that creature. Open this door. Don't expect nuance. The party can't ask it to "subdue without killing", because it has one combat verb and that verb is Slam. If a player tries to use it as a thinking ally, the golem stares blankly and follows the last clear order. That's the gag and the constraint.

In combat, position the golem in front of the party and let it absorb hits. Resistances to Bludgeoning, Piercing, and Slashing plus 123 HP and Magic Resistance make it the best meat shield they will ever borrow. Hasten on recharge gives them one round of three-Slam burst, which is the right round to commit the rest of the party's nova. The HP max reduction works on enemies just like it works on the party, so a single fight against a clay golem ally can permanently soften an elite enemy for the rest of a session.

The Berserk rule is the price. The first time the golem is Bloodied, the party rolls the d6 themselves. On a 6, the GM takes the golem back. That uncertainty makes the loan feel earned.

A clay golem is a slow, dumb wrecking ball with one terrifying mechanic: every Slam carries Acid damage that lowers the target's Hit Point maximum until a long rest. The party can't outheal it. They have to kill it before they run out of headroom on the cleric. Build the encounter around that pressure.

It walks at 30 ft. with no fly or burrow, so it should be in a place the party can't easily kite. A temple antechamber, a vault corridor, a guarded stair, anywhere with five-foot-reach geometry. Open with two Slam attacks at +9 (10 bludgeoning plus 6 acid each, target's HP max drops by the acid taken). Don't be subtle: announce the HP max reduction at the table the first time it lands. The fighter going from 60 maximum to 54 maximum should land like a slap.

Hasten (recharge 5-6) is the breakpoint. On the round it's available, the golem takes Dash and Disengage as a Bonus Action and makes three Slam attacks instead of two. Save it for the moment a wizard pulls back to range; one Hasten round closes 60 ft. and lands three Slams on the squishy. Bloodied, the golem rolls 1d6 each turn for Berserk; on a 6 it loses target priority and starts hitting whatever is nearest, including walls and pillars. That's a feature, not a bug. A berserk clay golem ripping through structural columns is exactly the kind of complication that turns a fight into a story.

The party will try to use Acid against it; that heals the golem (Acid Absorption). Telegraph this once. Magic Resistance gives Advantage on saves against spells, and resistances to Bludgeoning, Piercing, and Slashing mean nonmagical mundane weapons feel pointless. The path to victory is magic weapons, fire, force, lightning, or radiant. Make sure at least one party member has access before you put this fight on the board.

Don't roleplay the golem. Three Intelligence, one Charisma, no goals beyond its standing order. Describe it in object terms: it does not stop, it has a destination. The horror is the absence of mind, so write the absence in.