Swarm of Ravens

A swarm of ravens as ally is the witch's familiar host or the corvid druid's wild shape companions. The Morrigan-style framing works: an old woman in a black shawl arrives at camp, the ravens follow, she introduces herself by another name and offers three scraps of advice in exchange for a name they would rather forget. The swarm is hers and lends itself to the party for as long as the favor lasts.

Tactical use is reconnaissance and intimidation. Fly 50 ft., passive Perception 15, and the ability to scatter and reform makes ravens the best long-distance scouting tool short of a Find Familiar. Send the swarm over the keep wall, have it count the guards, return with a feather dropped at the wizard's feet. In a fight, the swarm flies into the enemy spellcaster's space and forces concentration checks on whatever ongoing spell would have ruined the party's day. Cacophony adds Wisdom saves for deafening, which breaks concentration indirectly.

Damage resistance to bludgeoning, piercing, and slashing means low-level enemies struggle to hurt the swarm, while a single Magic Missile or Burning Hands ends it in one cast.

The exit is the witch leaving. When the favor is done, she calls the swarm back with a single low whistle and walks out of camp without waiting for goodbyes. The ravens follow into the trees. If the party tries to keep one bird as a souvenir, the bird will be gone from the cage in the morning, and the cage will have a single black feather inside it.

Have one raven land on the gravest party member's shoulder and stay through a full scene of dialogue. The player will roleplay around it for the rest of the session.

A swarm of ravens is the omen made physical. AC 12, 11 HP, walk 10 ft., fly 50 ft., passive Perception 15. Beaks action deals 1d6+2 piercing damage, or 1d4 if bloodied. Cacophony is a recharge 6 Wisdom saving throw (DC 10) that inflicts the Deafened condition until the start of the swarm's next turn, with disadvantage on ability checks and attack rolls while deafened. The swarm is a hazard with feathers, not a damage-dealing combatant.

The opener is environmental. The swarm comes off a gallows tree, off a battlefield two days old, off the eaves of a haunted chapel. Passive Perception 15 means it notices the party at distance and decides whether to react. Use the swarm as a cloud that obscures vision and harasses casters. Any creature inside the swarm's space has disadvantage on concentration saves. The 50 ft. fly speed lets it intercept a courier, blot out moonlight on a roof, or shadow a guilty PC home for an evening.

Resistance to bludgeoning, piercing, and slashing means low-level enemies struggle to hurt the swarm, but a single Burning Hands or a swung torch ends the fight in one cast. Cacophony on recharge 6 adds a Wisdom save DC 10 for deafening, which can break a spellcaster's concentration indirectly.

Ravens scatter when half the flock is gone. Once bloodied at 5 HP, the swarm breaks into individual birds and disperses to rooftops, trees, the open sky. None die. They are watching the party from three different rooftops by the next scene, and the party can feel it.