Giant Hyena

A friendly giant hyena is a beast companion or a druid's wild-shape pick. Plausible framings: a Gnoll-defector NPC who keeps her old pack-mate as her one tie to a former life, a barbarian raised by hyenas who treats the beast like a sibling, a circus animal the party freed that now follows the bard with embarrassing devotion. Run it as a beast companion: low Int, no language, but capable of being pointed at a target and trusted to bite until something falls.

In combat, the hyena's job is the flanker, not the bruiser. With AC 12 and 45 HP, it will not survive direct attention from anything CR 2 or higher, so don't park it next to the enemy fighter. Use the 50 ft. walk speed to get behind archers and casters. Bite once at plus 5 for 2d6+3, and dart out before the enemy's next turn. If a target is already Bloodied, Rampage triggers: move up to 25 ft. and bite again. Two PCs and a hyena versus a single bandit captain is a clean kill in two rounds. The hyena dying changes the math; remember that AC 12 is light leather, and one critical from anything dangerous ends it.

Out of combat, the hyena is a tracker (passive Perception 13, Darkvision 60 ft., and a beast's nose), a deterrent at camp, and a comedy NPC. It eats anything organic, including the fighter's spare boots if they're left out. It laughs when nervous, which ruins every stealth check the party tries to make near it. Lean on the laughter as a recurring problem the party has to plan around. The first time it gives them away to a sleeping enemy, they understand what owning a giant hyena costs. Name the hyena. Ask the player who feeds it to come up with the name. They will hold the loss harder when something with sharper teeth eats it.

A giant hyena is a 50 ft. pack predator with Darkvision 60 ft. and passive Perception 13. Bite is plus 5 for 2d6+3 piercing. Rampage (1/day) lets the hyena move up to half its speed and make a Bite attack immediately after dealing damage to a Bloodied target. This is the pack predator's signature: close fast, bite a weakened target, move again with Rampage for a second bite in one turn.

Open at distance with a pack of three or four, called in by a single hyena's laugh from a ridge. The hyena's 50 ft. walk speed beats every PC's base movement, so the opening turn closes the gap and forces the party to react. Have the lead hyena lunge at the back-row caster while two more circle the fighter to keep them busy. Pack predators don't fight fair: target the wounded, target the small, target whoever is alone. A downed PC gets dragged 25 ft. away on the next hyena's turn while a third covers the retreat.

These are Unaligned beasts with Int 2. They don't recognize spells as a category, but they do recognize fire (run away from torches), thunder (flinch), and a creature that just dropped one of their own (target it next). Use the laugh as a recurring sound cue from the dark, even when the pack isn't in line of sight. Darkvision 60 ft. means they see the party long before the party sees them, and the laughter from outside the firelight is doing the work the stat block can't.

When the pack is below half its starting numbers, the survivors break and sprint 50 ft. away in random directions. They will be back at dawn or the next dusk, hungrier. If the party left bodies, the pack returns to the bodies.