Fey Ancestry. Yanna has advantage on saving throws against being charmed, and magic can't put the Yanna to sleep.

Regeneration. Yanna regains 10 hit points at the start of its turn if it has at least 1 hit point and isn't in sunlight or running water. If the vampire takes radiant damage or damage from holy water, this trait doesn't function at the start of the vampire's next turn.

Spider Climb. Yanna can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Vampire Weaknesses. Yanna has the following flaws:

Forbiddance. Yanna can't enter a residence without an invitation from one of the occupants.
Harmed by Running Water. Yanna takes 20 acid damage when it ends its turn in running water.
Stake to the Heart. Yanna is destroyed if a piercing weapon made of wood is driven into its heart while it is incapacitated in its resting place.
Sunlight Hypersensitivity. Yanna takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

Spellcasting. Yanna is an 8th-level Druid spellcaster. Her spellcasting ability is Wisdom (spell save DC 14, +6 to hit with spell attacks). Yanna has the following druid spells prepared: 

• Cantrips (at will): poison spray, shillelagh, thorn whip

• 1st level (4 slots): cure wounds, entangle, ray of sickness

• 2nd level (3 slots): pass without trace, ray of enfeeblement, spike growth

• 3rd level (3 slots): animate dead, dispel magic, plant growth

• 4th level (2 slots): blight, giant insect

Bite of Decay. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target, one willing creature, or a creature that is grappled by Yanna, incapacitated, or restrained. Hit: Hit: 9 (2d8) Poison damage, and the target must make a DC 14 Constitution saving throw, taking 8 (2d8) necrotic damage on a failed save, or half as much damage on a successful one. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, and Yanna regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.