Ancient Vampire (Grim Hollow Base)

Legendary Resistance. (3/Day).  If the vampire fails a saving throw, it can choose to succeed instead. 

Regeneration. The vampire regains 25 hit points at the start of its turn if it has at leat 1 hit point. If the vampire takes radiant damage, it regains 10 hit points from the next use of this trait instead.

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

Vampire Weakness. The vampire has the following flaws: Forbiddance. The vampire can't enter a residence without an invitation from one of the occupants. Stake to the Heart. The vampire dies if a piercing weapon made of wood is driven into its heart while it is incapacitated in its resting place. 

Multiattack. The vampire makes three attacks, only one of which can be a bite.

Claws. Melee Weapon Attack. +11 to hit, reach 5 ft., one target. Hit: 15 (2d8 + 6) slashing damage. If the target is a creature, the vampire can grapple the target. (escape DC 19).

Bite. Melee weapon attack: +11 to hit, reach 5ft., one creature. Hit: (2d8 + 6) piercing damage and 17 (5d6) necrotic damage. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken,  and the vampire 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. A humanoid slain in this way and then buried rises the following night as a vampire spawn under this vampires control. 

Beast Form. If the vampire isn't in sunlight, it polymorphs into a medium or smaller beast, usually with thangs and claws, or back into it's true form.  While in beast form, the vampire can gain a fly or swim speed of 30 feet, but its other statistics remain the same. If the new form lacks claws, the vampire can make slam attacks that deal the same amount of bludgeoning damage. Anything it wears transforms with it, but nothing it is carrying does. It reverts to its true form if it dies.

Mist Form. If the vampire isn't in sunlight, it polymorphs into a medium cloud of mist, or back into its true from. Anything it wears of carries transforms with it. While in mist form, the vampire can't take any actions, speak, or manipulate objects. It is weightless, has a flying speed of 120ft., can hover, and can enter a hostile creature's space, the mist can do so without squeezing, but it can't pass through water. It has advantage on Strength, Dexterity, and Constitution saving throws. A vampire in mist form is immune to nonmagical damage, except damage from sunlight, and has resistance to damage other than radiant. The vampire reverts to its true form if it dies.

Misty Escape.  When it drops to 0 hit points outside of its resting place, the vampire transforms into its mist form instead of falling unconscious.If the vampire can't t transform it dies. While it has 0 hit points in mist form, the vampire dies if it takes damage three times or radiant damage once. It can't willingly revert to its vampire form, and it must reach its resting place within 2 hours or die. Once in its resting place, it reverts to its vampire form. It is then paralyzed until it regains at least 1 hit point. After spending 1 hour in its resting place with 0 hit points, it regains 1 hit point. 

The vampire can take 3 legendary actions, choosing from the options here. Only one legendary action option can be used at a time and only at the end of another creatures turn. The vampire regains spent legendary actions at the start of its turn. 

Move. The vampire moves up to its speed without provoking opportunity attacks.

Claws. The vampire attacks once with its claws. 

Bite (2 Actions). The Vampire makes one bite attack.

Purify Blood (2 Actions). Even if the vampire can't take actions, one condition ends on it.