Arckenbury Hag (Serrah)

Swamp Walker. Maria can breathe air and water, and moves through swampland as though it were not difficult terrain.
Draining Aura. Any non-fey creature that starts its turn within ten feet of Serrah must succeed on a DC 12 Constitution saving throw or take 10 [roll]4d4[/roll] necrotic damage, and Serrah gains temporary hit points equal to half the total necrotic damage dealt in this way.
Coven Spellcasting. While all three members of the Arckenbury Coven are within 50 feet of one another, they can each cast the following spells. For casting these spells, each hag is a 4th-level spellcaster. Their spellcasting ability is Intelligence (spell save DC 12, [roll]1d20+4[/roll] to hit with spell attacks). They have the following wizard spells prepared but must share the spell slots among themselves:
1st level (5 slots): identify, mage armor*, shield
2nd level (4 slots): alter self, scorching ray, web
*Each of the Arckenbury coven has already cast mage armor prior to
meeting the adventurers, leaving only one 1st level spell slot.

Bite. Melee weapon attack: [roll]1d20+2[/roll] to hit, reach 5 ft., one target. Hit: 7 [roll]2d6[/roll] piercing damage.
Luring Song. Serrah sings an entrancing song in a strange and unsettling ancient language. Every living, non-fey creature within 300 feet of Serrah that can hear the song must succeed on a DC 12 Wisdom saving throw or be charmed until the song ends. Serrah must take a bonus action on her subsequent turns to continue singing. She can stop singing at any time, and the song ends if she is incapacitated.
    While charmed by Serrah, the target must spend its movement action to move towards her in the most direct route possible, even if doing so results in opportunity attacks or other dangers. If the charmed target attempts to attack Serrah, it must succeed on a DC 12 Intelligence saving throw or become afflicted by a form of temporary madness.
    A creature repeats its DC 12 Wisdom saving throw at the end of each of its turns to end the charmed effect. A target that successfully saves against the song is immune to its effects for the next 24 hours.