Blood Thirster

Siege Monster. The Blood Thirster deals double damage to objects and structures.

Unimpedeable. The Blood Thirster is unaffected by rough terrain, magical or natural, and it's speed is unable to be reduced once it has turned aggressive. Additionally, the Blood Thirster can pass through the spaces of creatures or object that are at most the same size as it without suffering a movement penalty.

Rapid Regeneration. The Blood Thirster regains 25 hit points at the start of each of it's turns. If the Blood Thirster take damage from a weapon made of Obsidian or takes damage from fire, this trait does not function at the start of the Blood Thirster's next turn. The Blood Thirster dies only if it starts its turn with 0 hit points and doesn’t regenerate.

Turn Immunity. The Blood Thirster is immune to effects that turn undead.

Eyes of the Blood Thirster. A creature within 60 feet of the Blood Thirster must make a DC 19 Wisdom saving throw or look it in the eyes. Which will add said creature to it's list of targets. The creature making this saving throw does not need to be aware of the Blood Thirster's presence to make the saving throw. Being added to the Blood Thirster's target list means that it will relentlessly chase down and attempt to kill anyone or anything that has looked it in the eyes.

Vengeful Tracker. The Blood Thirsters knows the distance and direction of any creature that looked it in the eyes, even if the creature and the Blood Thirster are on different planes of existence. If the creature being tracked by the Blood Thirster dies, the Blood Thirster knows and will become passive if it has no more targets to track.

Aggressive Movement. When the Blood Thirster has at least one creature it is able to track it's movement speed and capabilities suddenly and drastically change. It's walking speed becomes 80 and it gains it climbing, swimming, and burrowing speed equal to it's walking speed.

Multiattack. The Blood Thirster makes two attacks with it's claws and one with it's bite. It may also replace it's bite attack with a swallow.

Claw. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) Slashing damage.  If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained.

Bite. Melee Weapon Attack: +10 to hit, reach 5 ft, one target. Hit: 36 (4d12 + 10) Piercing damage.

Swallow. The Blood Thirster makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, the target takes the bite’s damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the Blood Thirster, and it takes 27 (6d8) acid damage at the start of each of the Blood Thirster’s turns.

If the Blood Thirster takes 40 damage or more on a single turn from a creature inside it, the Blood Thirster must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the Blood Thirster. If the Blood Thirster dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Vicious Devour. If a creature is reduced to 0 hit points within 60 feet of the Blood Thirster it can use it's reaction to move up to it's movement speed without provoking attacks of opportunity to attempt to devour that creature. Once the Blood Thirster is within 5 ft. of the target it makes a bite attack against the creature and swallows it if it hits. This also causes the Blood Thirster take regain hit points equal to the target's constitution score.