Vampiric Tyrannosaurus Rex

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

Regeneration. The Vampiric Tyrannosaurus Rex regains 20 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 Vampiric Tyrannosaurus Rex takes radiant damage or damage from holy water, this trait doesn’t function at the start of the it's next turn.

Vampire Weaknesses. The Vampiric Tyrannosaurus Rex has the following flaws:

Harmed by Running Water. The Vampiric Tyrannosaurus Rex takes 20 acid damage if it ends its turn in running water.

Stake to the Heart. If a piercing weapon made of wood is driven into the Vampiric Tyrannosaurus Rex's heart while the Vampiric Tyrannosaurus Rex is incapacitated it is paralyzed until the stake is removed.

Sunlight Hypersensitivity. The Vampiric Tyrannosaurus Rex takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

Multiattack. The Vampiric Tyrannosaurus Rex makes two attacks: one with its bite and one with its tail. It can't make both attacks against the same target.

Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 34 (4d12 + 8) piercing damage plus 10 (3d6) necrotic damage. The target’s hit point maximum is reduced by an amount equal to the necrotic damage taken, and the Vampiric Tyrannosaurus Rex 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 in the ground rises the following night as a vampire spawn. If the target is a Medium or smaller creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the Vampiric Tyrannosaurus Rex can't bite another target.

Tail. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 26 (4d8 + 8) bludgeoning damage. If the target is a Medium or smaller creature, it is knocked prone if it fails a DC 20 Strength saving throw.