Blood Rose, Vessel of Rebirth

Demolith Subtype. The rose has the "(demolith)" tag, which has no rules of its own, but is a tag that affects the rose in the same way that it would affect a demon or devil.

Fiend Subtype. The rose has the "(Fiend)" subtype, which has no rules of its own, but makes it so that the rose is considered both a Plant and a Fiend at the same time. This means that a effect that would affect only Fiends or only Plants, it would affect the rose either way.

Semi-Immortal Nature. The rose can't die of old age unless affected by magic of a spell of 6th level or higher and doesn't require food, drink, air, or sleep.

Minor Legendary Resistance (1/Day). If the rose fails a saving throw, it can choose to reroll it with advantage.

Multiattack. The blood rose makes two Tendril attacks and one Bite attack. Alternatively, the rose makes four Hellish Breath attacks.

Acidic Multiattack (Usable Only When at Half-Hit-Points, Recharge 4-6). The rose uses its Acidic Glob attack six times.

Tendril. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 9 (1d10 + 4) piercing damage + 2 (1d4) poison damage.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 18 (2d12 + 4) piercing damage + 4 (1d8) poison or necrotic damage (rose's choice).

Hellish Breath. Ranged Spell Attack: +5 to hit, range 120 ft., one target. Hit: 7 (2d6) necrotic damage. On a critical hit, the rose can push the target, if it is creature, up to 10 feet in a random direction.

Acid Glob. Ranged Spell Attack: +5 to hit, range 80 ft., up to two targets each within 10 ft. of each other. Hit: 10 (3d6) acid damage.

Tongue. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 9 (1d8 + 4) piercing damage and the target is grappled (escape DC 17) and the rose can make a Bite attack against it as a bonus action. If the Bite attack hits, the target is also restrained until the grapple ends.

Spikefield. The rose causes a 20-foot wide, 40-foot long line across the ground of blood-red spikes originating at three points it can see within 15 feet of it. Each target caught in the line must make a DC 16 Dexterity saving throw, taking 12 (5d4) piercing damage + 4 (1d8) necrotic damage on a failed save, or half as much on a success.

Summon Roots (Recharge 5-6). The rose causes 2d4 yellow musk creepers, with a Bite attack instead of Touch attack that deal piercing damage instead of psychic damage, to appear at separate points within 60 feet of the rose. A summoned creeper remains for 1 minute or until it or the rose are killed, acts as an ally of the rose and takes its turn immediately after the rose's.

Bloodbound Beam (Recharge 6). The rose unleashes a 5-foot wide, 80 foot long line of toxic necrotic energy and vomitous blood. Each target within the area must make a DC 17 Dexterity saving throw, taking 32 (5d12) necrotic damage + 11 (2d10) acid damage.

Horrific Sprouting (Usable Only When at Half-Hit-Points). The rose causes its numerous spiky-mawed roots and vines to erupt from the ground for 1 minute all around it in a 20-foot radius. At the start of each creature's turn, any target within the area must succeed on a DC 18 Dexterity saving throw, taking 11 (1d12 + 5) piercing damage + 4 (1d8) poison damage on a failed save, or half as much damage on a success. Additionally at the start of each creature's turn, all creatures within 60 feet of the area must succeed on a DC 14 Strength saving throw or be forcefully moved 5 feet toward the blood rose.

Life Drain (Recharge 4-6). The rose targets a creature it can see within 40 feet of it. That creature must make a DC 14 Constitution saving throw, being paralyzed and take 5 (1d10) necrotic damage at the start of each of its turns for 1 minute on a failure, or have its speed decreased by 5 feet and take 1 necrotic damage at the start of each of its turns for 1 minute on a success. Whenever a creature loses hit points from the rose's Life Drain, the rose or its master The Countess (Countess's choice) regains hit points equal to the amount of necrotic damage dealt. 

Lively Burst (Usable Only When at Half-Hit-Points, 1/Short or Long Rest). In reaction to regaining hit points, the rose unleashes a powerful burst of energy. Each creature hostile to the rose within 30 feet of it must succeed on a DC 19 Strength saving throw or take 7 (2d6) necrotic damage and be stunned until the end of that creature's turn.

The rose can take 1 legendary action, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The rose regains spent legendary actions at the start of its turn.

Sense. The rose's Passive Perception increases by 5 for 5 minutes.

Acid Pool. The rose forms a toxic pool of bile to form from the disintegrating earth around a creature it can see within 40 feet of it, which lasts until the end of the next round. At the start of each of that creature's turns, it must succeed on a DC 15 Constitution saving throw or take 9 (2d8) acid damage.