Bloodstain Mimic

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

Blood Frenzy. The Bloodstain Mimic has advantage on melee attack rolls against creatures that are not at full Hitpoints.

Magic Resistance. The Bloodstain Mimic has advantage on saving throws against spells and other magical effects.

Relentless. If the Mimic would be reduced to 0 hit points, there is a chance that it can instead only be reduced to 1.

Shapechanger. The mimic can use its action to polymorph into an object or back into its true, amorphous form. Its statistics are the same in each

False Appearance (Bloodstain form only). While the mimic remains motionless, it is indistinguishable from an ordinary pool of blood, or a corpse.

Wounding. Hitpoints lost to the Mimics Bite and Claw attacks can be regained only through a short or Long Rest, rather than by regeneration, magic, or any other means as the Mimic steals blood. Once per turn, when the Mimic hits, It can wound one target, at the start of the wounded creatures turn, it takes 1d4 necrotic damage for each time it  has been struck by the Mimic, It can then make a DC 15 Constitution saving throw, ending the effect of all such wounds on itself on a success. Alternatively, the wounded creature, or creature within 5 ft of it, can use an Action to make a DC 15 Wisdom (Medicine) check, ending the effect of such wounds on it on a success. If the wounded creature is within 5-10ft of the Mimic, it restores 1/4 hitpoints of the damage dealt from the wounding.

Multiattack. The Bloodstain Mimic can use its Frightful Presence. It then makes three attacks: one with its bite, two with its claws. It can use its Swallow instead of its bite.

Frightful Presence. Each creature of the Mimics choice within 60 feet of it and aware of it must succeed on a DC 17 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the Mimic is within line of sight, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the Mimics Frightful Presence for the next 1d10 hours.

Bite. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 7 (1d8 + 3) piercing damage plus 4 (1d8) acid damage.

Claws. Melee Weapon Attack: +3 to hit, reach 10ft., one target. Hit: 28 (4d8 + 10) Acid/Slashing damage. Successful attacks when it draws blood heals the Mimic with 1/4th the damage dealt.

Swallow. The Mimic makes one bite attack against a Medium 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 Mimic, and it takes 28 (8d6) acid damage at the start of each of the Mimics turns. If the target creature expires while swallowed, another Bloodstain Mimic will be created within 1d6 hours.

If the Mimic takes 30 damage or more on a single turn from a creature inside it, the Mimic 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 Mimic. If the Mimic dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Swallowed creatures must do a DC 15 Constitution saving throw upon receiving damage while swallowed, upon success, the Bloodstain Mimic does not regain health, on failure, the Bloodstain Mimic regains 1/4 the damage dealt by Acid.

The Bloodstain Mimic can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The Bloodstain Mimic regains spent legendary actions at the start of its turn.

Attack. The Mimic makes two Bite Attacks, and can use its action to swallow a creature.

Claws. The Mimic makes two Claw Attacks.