Blood Hound

Amorphous. The Blood Hound can move through a space as narrow as 1 inch wide without squeezing.

Blood Draw. When a creature is grappled by a Blood Hound, it takes damage at the start of their turn until they break the grapple. This damage depends on the size of the Blood Hound. 1d6 if the Blood Hound is tiny (under 10 hit points), 1d8 if the Blood Hound is small  (11-30 hit points), 2d8 if the Blood Hound is medium ( 31-75 hit points), 2d10 if the Blood Hound is large ( 76-100 hit points), 4d12 if the Blood Hound is giant (101-125 hit points), 8d12 if the Blood Hound is gargantuan (>126 hit points) . The Blood Hound gains hit points equal to the damage dealt.

Improved Stats. When the Blood Hound increases in size its physical stats increase by   2 for each size above tiny.

Leech. Melee Weapon Attack: +4 to hit, reach 60ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage plus 7 (2d6) necrotic damage. The Blood Hound moves to occupy the same space as the target and the target is grappled, DC 15 to escape.

Improved Leech. When the Blood Hound is considered Medium or larger, it can benefit from the Improved Leech. Melee Weapon Attack: +7 to hit, reach 60ft., two targets. Hit: 4 (1d8+1) bludgeoning damage plus 7 (2d8) necrotic damage. The Blood Hound pulls the targets to occupy the same space as itself (DC 17 to resist) and the target is grappled, DC 17 to escape. The Blood Hound's damage dice increase by one level each size above medium.

Cut. As a reaction to being hit, the Blood Hound can deal its normal blood draw damage.

Engulf. When the Blood Hound is one size larger than the creature it is grappling, it can use 1 legendary action to fully engulf the target doing twice the normal blood draw damage. The target is considered restrained.