Ape

A trained ape on the party's side is the ranger's animal companion, the druid's wild-shape favorite, or a circus performer the party rescued from a cage. Treat it as a strong dumb friend with a 30 ft. climb speed and a +5 Athletics. It will not understand verbal plans more complex than "stay" and "come", so the player who handles it should declare the ape's intent at the top of each round, not in the middle of a turn.

The ape's combat utility is positional, not damaging. Send it up trees, walls, or rigging to reach archers and casters who think they're safe behind cover. With Athletics +5 against most enemies' Dex or Str, it wins most grapple contests against Medium foes, which lets the party shut down a single high-priority enemy without spending a spell. Pair it with a rogue who needs the +2 from a grappled target, or a barbarian who wants the prone they get after the shove. Strength 16 is good but not great, so don't expect it to manhandle anything Large.

With 19 HP and AC 12, the ape folds fast against any organized opposition. Pull it out of melee the moment two enemies turn their attention to it. A dead companion is a sad scene, and a dying one in the middle of an adventure burns table time on a side decision the player didn't sign up to make.

If the player wants the ape to feel like a real character, name something it loves and something it fears. A stolen apple becomes a recurring bit. A campfire makes it nervous and the player has to coax it across.

A wild ape is a territory encounter. The party is moving through jungle, ruins, or a forested mountainside, and the ape has decided they are too close to its tree, its mate, or its food. It is not trying to kill them. It is trying to make them leave, and the fight ends the moment they back off ten paces and stop making eye contact.

Open with a display, not an attack. The ape drops from the canopy using its 30 ft. climb speed, beats its chest, and only swings if the party doesn't read the warning. With Passive Perception 13 and +3 Perception, it spotted them long before they spotted it, so the GM gets to choose when the encounter triggers. Place the ape on high ground or in branches above the trail. Athletics +5 lets it grapple a player and drag them up into the trees if the encounter needs a sharper hook than a straight brawl.

In a true fight, AC 12 and 19 HP are not going to last past one round of focused damage from a level-3 party. So either run two or three apes together as a troop, or play this one as a single ambush meant to soften the party before something worse comes through the same canopy. Once it drops below half HP, it should retreat fast, climb up a tree, vanish, watch from cover. Apes do not die for territory they can re-claim later.

Resolve the encounter with consequence, not a corpse. If the party kills the ape, mention the carrion eaters that arrive within minutes. If they back off, give them a moment of being watched from the trees for the next mile.