Blight

Necrotic Origin. The origins of this blight is unknown and it acts both like an ooze and an undead. It has blindsight out to 300ft, and is blind beyond this point. It also gains immunity to necrotic damage, turning this damage into healing equal to the necrotic damage dealt.

Sunlight Sensitivity

The blight has disadvantage on attack rolls and on Wisdom (Perception) checks that rely on sight when they, the target of their attack, or whatever they are trying to perceive is in direct sunlight.

Necrotic Magic

The blight can use its innate Necrotic Magic, using their Charisma as their spellcasting ability, DC 20:

At Will: chill touch 

5 slots/day: vampiric touch, false life 

Shape-changing

The Blight can change it's physical shape to accommodate different purposes, feeding off of different emotions. In combat, the following four forms seem common:

Anxiety. While in this form, the blight can't make any attacks. The blight's movement speed is halved and it has disadvantage on Dexterity Saving Throws. It gains immunity to all damage types apart from radiant, which remains vulnerability. While in this form, any attack made against the blight is rebuked, reflecting the damage back onto the creature that dealt it. Ignoring any and all resistances and treating immunities as resistances, the creature that dealt damage to the pain blight receives the same amount of damage in return.

Fear. While in this form, everyone within a 20ft radius must succeed on a DC 20 Wisdom Saving Throw or become frightened. While frightened in this way, the creature's movement speed becomes 0 if the blight is in the creature's line of sight. The blight has advantage on attack rolls against frightened creatures. When landing a critical hit on a creature, the target must make a further DC 20 Wisdom Saving Throw or spend their next turn attacking the nearest creature, whether friend or foe, swinging blindly in fear. The target must then make another DC 20 Wisdom Saving Throw every time they attack blindly in this way, allowing the opportunity to overcome the fear flowing through them.

Hatred. While in this form, the blight gains 10 temporary hit points each time it makes an attack with its Necrotic Tendril attack and can enter a rage-like state, in which it deals 10 more necrotic damage with each attack. The blight also gains the ability to taunt a creature within 30 feet of it as a bonus action. The target must make a DC 20 Wisdom Saving Throw or gain the frenzy state, in which they recklessly attack, gaining advantage on the attack, but also granting any attacks against themselves advantage. They can reroll the Wisdom Saving Throw at the end of each of their turns. If this remains for 5 turns or more, they must make another DC 20 Wisdom Saving Throw at the start of their turn or become blind with hatred. Their attacks deal an additional 2 damage, but they have disadvantage on all Saving Throws and attacks against any target besides the blight. If this blinding hatred remains for 2 or more turns, they take psychic damage at the start of each turn equal to a number of d6s equal to the number of rounds this blinding hatred has been active, starting at 2d6, ending at a total of 20d6, after which the blinding hatred automatically ends. To overcome the blinding hatred, the creature must use their action to roll a DC 16 Wisdom Saving Throw to overcome the blinding hatred. This form feeds off of hate for the living, becoming a brute that aims to do nothing but inflict as much pain as possible.

Loss. While in this form, the blight loses all resistances it has, opening itself to attacks. However, the more it is damaged, the more frenzied and desperate it becomes. Every creature within 20 feet of the blight must make a DC 20 Constitution Saving Throw or take necrotic damage equal to half the hit points that the blight is missing at the start of their turn. The blight also gains two additional attacks in its multi-attack if it is under half hit points.

Lust. While in this form, the blight gains two more attacks to it's multi-attack action, using both only for Necrotic Tendril attacks. The Necrotic Tendril attacks are also now able to grapple enemies. Grappled enemies takes necrotic tendril damage on subsequent turns that the creature remains grappled for and the blight can move the target freely up to 30 feet as a bonus action on subsequent turns that the creature remains grappled. On top of this, when the blight makes a melee attack against a creature, it doesn't provoke opportunity attacks from that creature for the rest of the turn, whether it hits or not.

Power-Hunger. While in this form, the blight can use an action to attempt to grapple a creature within 30 feet of it. If successful, it can then use its bonus action on the same turn to consume the creature. The creature must make a DC 20 Constitution Saving Throw to resist being consumed. If the blight consumes a creature, it gains temporary hit points equal to the creature's remaining hit points, or twice as much if the blight is under half hit points. The blight then gains advantage on its attacks until the creature succeeds the Constitution Saving Throw, rolling once at the end of each of their turns, but all attacks against the blight have advantage. The blight also gains the benefit of a +8 bonus to damage rolls with its natural weapons. The creature consumed by the blight must make a DC 16 Constitution Saving Throw at the start of its turn, taking 8d8 necrotic damage on a failed save, or half as much on a successful save. A consumed creature has disadvantage on attack rolls but can take actions as normal. At the end of a consumed creature's turn it must make another DC 20 Constitution Saving Throw to break free from the blight. If a creature remains consumed for 5 rounds or more, it becomes poisoned until its next rest and cant heal while under this effect.

The blight must use it's action and bonus action to start transforming from one form to another. The blight then takes 2 rounds to transform. During this time, the blight can not make actions, bonus actions, nor reactions, its AC equals 22 and it's speed is 0ft as it encases itself in a thick-layered cocoon. The blight can be interrupted in this process, as if concentrating on a spell, but has advantage on any Con saves made in this way. The blight then needs to recharge this ability [Recharge 5-6] in order to transform again.

Multiattack. The blight makes two attacks, mixing spells and natural weapon attacks.

Necrotic Tendril. Melee Weapon Attack: +12 to hit, reach 30 ft., one target. Hit: 27 (3d12 + 7) necrotic damage.

Necrotic Spit. Ranged Weapon Attack: +12 to hit, ranged 100/400 ft., one target. Hit: 18 (2d10+7) necrotic damage. Hit: 13 (1d10+7) piercing damage.

Vengeful Rebuke. As a reaction, the blight can make an extra natural weapon attack against a creature that has dealt more than 20 points of damage to it in one turn.