Night Hag

Allied night hags happen when the party needs something only a Neutral Evil planar broker can deliver: a soul released from another hag's bag, a binding contract enforceable across planes, knowledge of where a specific Sleeping King's dream is held tonight. The hag will deal, but she charges in souls or favors of equivalent weight, and she keeps the receipts.

In a fight on the party's side, the hag is a force multiplier rather than a frontliner, which is exactly how she likes it. Magic Missile (level 4 version) at-will every round is reliable damage at no resource cost. Phantasmal Killer (2/day, DC 14 Wisdom for 4d10 psychic plus Frightened) lands on the enemy's heaviest hitter and removes them from the round. Etherealness lets her relocate around the battlefield without provoking, repositioning to whatever flank the party needs flanked. She will not enter melee for the party. Claws are for problems she could solve another way, and night hags do not solve problems with their hands when their voice will do.

The contract is the encounter. The hag's price is named up front and is always slightly more than the party wants to pay, because the second cost is what makes the alliance interesting. She will not ask for a soul on day one; she will ask for a memory, a name, a year off the youngest PC's life. Whatever she takes, write it on the campaign sheet. When she returns three sessions later to collect a different debt, the party will already feel the weight.

Have the hag refer to one PC by their childhood nickname the first time she greets them. She read it off their sleeping mind last week and the player just learned how thin the wall is.

A night hag is a long-game antagonist whose stat-block fight is the smaller half of the encounter. The bigger half is the soul bag and the Ethereal commute. Run the hag as a monster who is mostly not in the same room as the party until she chooses to be, and the campaign starts feeling like horror instead of a CR 5 brawl.

Before any combat, the hag is on the Ethereal Plane casting Etherealness in and out as a free at-will spell. She uses Nightmare Haunting once per day to cast Dream on a sleeping party member: that's a soul-bag-required attack that, on a fail, drops the target's HP maximum by the damage taken and traps the soul if it kills them. Stack three or four nights of this against the party's caster and she's lowered them ten HP max before the players have heard the word "hag." When the fight happens, Magic Resistance (Advantage on saves vs spells) plus AC 17 and 112 HP make her sticky, and her Plane Shift (self only, 2/day) is the escape valve that ensures she lives to haunt next week.

In active combat, the engine is Multiattack: two Claw attacks at +7 for 2d8+4 each, averaging 26 per round of melee. Her at-will Magic Missile (level 4 version) is the reliable damage filler, ten force darts auto-hitting the squishiest PC. Phantasmal Killer, 2/day, is the kill button: DC 14 Wisdom save, then DC 14 Wisdom save again on the hag's turn for 4d10 psychic, and Frightened in between. Aim it at the cleric. If she has two hag allies within 30 ft., Coven Magic opens up Augury, Find Familiar, Identify, Locate Object, Scrying, and Unseen Servant once each per long rest, which is more useful for the campaign than the round.

Run her retreat aggressively. At Bloodied, she goes Etherealness as her action and is gone, the Soul Bag still on her belt. The party never gets the bag without finding her lair on the Ethereal Plane. Set up that hunt as an arc.

Do the Dream attacks at the start of session, in second person, to the player whose PC was sleeping. They will remember every word.