Slimelius

(Note: As you will read later on, Slimelius damages himself with most of his attacks, so the 1000 HP isn't as OP as it seems)

Passive effects
Membrane: A layer of his gel has solidified on his surface. Although the inner gel won’t pour out if it is pierced, and it is really only used as a defensive layer.

Disintegration gel: Making contact with the outer membrane will hurt you for 1d12 of acid damage for every round in contact, dealing the damage on initial contact and then for every round. The inner gel will disintegrate things faster and deals 1d4 for every turn of each creature inside in contact, on initial contact and then every turn afterwards. The inner gel’s disintegration will also destroy non-living things, completely disintegrating: Cloth in about 1 turn, wood in 2 turns, stone in 1 round, weak nonmagical metals in 1 round (Iron, lead, etc.) strong metals in 2 rounds (Adamantine?, Mithral?) and it won’t disintegrate anything stronger than that or crystals. Disintegration gel does not take effect during engulf.

Slime slices: In intervals of 25 damage (Not necessarily all at once), Slimelius creates a Teal Slime. Although the slime itself isn’t necessarily that dangerous, they can overwhelm you if you aren’t careful. Self-inflicted damage (From the various attacks) does not turn into Teal Slime.

Legendary Resistance 5/day

Chaotic Presence: Wherever Slimelius goes, chaos follows. In a 120 feet radius, at the start of any turn, everything must succeed a DC23 constitution check or their alignment will become chaotic until Slimelius leaves or they succeed on the check.

Siege Monster: 4x damage on residential structures not made of steel.

Actions
Spell create: Deals 25 damage to Slimelius and automatically stores a 9th level spell in his crown. Slimelius can only do this once every five turns and always will unless he is under 100 hp

Spell cast: Casts the spell Slimelius stored in his crown.

Hyperjump: Slimelius jumps 60 feet into the air, and then lands down 40 feet from wherever he first jumped. This is his main form of attack.

Engulf: Slimelius explodes himself and as such, turns into a thin layer of gel on the ground within a 1-mile? Radius. Each part of Slimelius that explodes out deals 1d20 bludgeoning unless players make a DC 20 Dexterity saving throw. After a few seconds, the gel begins to move towards wherever the crown landed, taking things with it and likely destroying things in its path. Anyone caught in the gel must succeed on a DC 21 strength or dexterity check, or use some item to escape (i.e. Insta Fortress). When Slimelius reforms, he loses 2d20 of hp due to gel loss. If the membrane was previously broken, it is now repaired.

Gel Geyser: Slimelius breaks part of his membrane and focuses gel in that area to make a jet of gel. Although the jet itself doesn’t do damage, the gel it is made of still does disintegration damage. The attack lasts 5 seconds, and when it is finished, the gel that was lost recollects in the same way it does in Engulf, just without repairing the membrane. This attack deals 1d12 damage to Slimelius.

Slime Absorption: Any Teal Slimes within 10 feet of Slimelius are absorbed into him, healing 10 hp each.

Nebula shift


Upon reaching 100 hp, Slimelius will use Slime Absorption and then use Nebula Shift. In Nebula shift, Slimelius’s gel starts to look similar to the night sky, with a general dark purple color and bright stars within him. Other changes in Nebula shift are that Slime Slices no longer works, Slimelius shrinks to 35 ft tall, and disintegration deals twice as much damage. Engulf is no longer used, and Slimelius’s speed becomes 20 normally (without jumping) and 100 during the jump. Slimelius also gains 2 new attacks:

Star shot: In Nebula Shifted form, Slimelius shoots out a star. The star will deal 1d100 - 10 force damage to anything that is hit. If the damage is 0 or less, then the damage dealt is 1.

Out with a bang: When Slimelius dies, he is granted temporary invulnerability to use this attack (This is the only action done during the invulnerability period). Slimelius explodes in the same way he does during engulf, except a 1/3rd mile radius and he doesn’t recollect. The stars in his gel then collect around his crown, and then float over to whoever dealt the finishing blow, and finally, bestow the crown upon the person and disappear.

Legendary Actions (5/day)

Jump: Slimelius jumps, with the effect of hyperjump.

Tentacle of Terror: Slimelius shoots out a tentacle of ooze, scattering 1d10 teal slimes and this attack:

Tentacle

+19 to hit, reach 20 ft, one target:

On a hit, Slimelius deals 3d10 + 5 bludgeoning and 3d12 acid damage, and the creature must succeed on a DC 23 Wisdom saving throw or be frightened for 1 minute.

Regrowth (costs 3 actions)

Slimelius absorbs all teal slimes in the area, regaining health equal to their total and growing in size if any is lost.