Innate Spellcasting. The wispmother's innate spellcasting ability is Charisma (spell save DC 14, +6 to hit with spell attacks). She can innately cast the following spells, requiring no spell slots:
Mirror Image. When the wispmother casts mirror image, rather than her rolling a d20 on a hit, her AC increases by +2 for each remaining duplicate. On a hit a duplicate is always destroyed. Otherwise the spell works as normal. Incorporeal Movement. The wispmother can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object. Sunlight Sensitivity. While in sunlight, the wispmother has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight. Cold Missiles. The wispmother's magic missile deals frost damage instead of force.
Wispmother's Kiss. Melee Spell Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) frost damage. Become Ethereal. The wispmother moves from the material plane to the ethereal plane or vice versa. Luring Song (Material only). The wispmother sings a magical melody. Every humanoid within 300 feet of the wispmother that can hear the song must succeed on a DC 14 Wisdom saving throw or be charmed until the song ends. The wispmother must take a bonus action on its subsequent turns to continue singing. It can stop singing at any time. The song requires concentration and ends if the wispmother is incapacitated. While charmed by the wispmother, a target is incapacitated and ignores the songs of other wispmother's. If the charmed target is more than 5 feet away from the wispmother, the target must move on its turn toward the wispmother by the most direct route, trying to get within 5 feet. It doesn't avoid opportunity attacks, but before moving into damaging terrain, such as lava or a pit, and whenever it takes damage from a source other than the wispmother, the target can repeat the saving throw. A charmed target can also repeat the saving throw at the end of each of its turns. If the saving throw is successful, the effect ends on it. A target that successfully saves is immune to this wispmother's song for the next 24 hours.
Soul Trap (Ethereal only). The wispmother touches a creature that has died in the last minute, at that moment a Wisp is created. The dead creatures soul becomes trapped as if under the affect of a soul trap spell and cannot be revived by any means until the wisp has been killed, upon which the soul is released. A dead creature that's soul has already been trapped by a soul trap spell or other similar effect cannot suffer this affect.