Legendary Resistance (3/Day). If SCP-3000 fails a saving throw, it can choose to succeed instead.

Siege Monster. SPC-3000 deals double damage to objects and structures (included in Tidal Wave).

Slimed Body. Whenever a creature comes into contact with SCP-3000 on its own, with a melee attack, or by being attacked by SCP-3000, that creature must make a Constitution saving throw DC 20 or be poisoned by the substances in the slime SCP-3000 secretes.  The slime has the same effect as the feeblemind spell.  Immunity to poison is immunity to this effect and this can be cures by a greater restoration spell or stronger magical cure.  Also an antidote could be concocted with a sample of this slime with one vial able to make one dose.  It is a DC 20 herbalism kit or alchemist's kit check.

Multiattack. SCP-3000 makes two attacks: one with its slam and one with its tail.

Slam. Melee Weapon Attack: +16 to hit, reach 20 ft., one target. Hit: 15 (1d10 + 10) bludgeoning damage plus 5 (1d10) acid damage.

Tail. Melee Weapon Attack: +16 to hit, reach 20 ft., one target. Hit: 16 (1d12 + 10) bludgeoning damage plus 6 (1d12) acid damage.

Tidal Wave (Recharge 6). While submerged, SCP-3000 magically creates a wall of water centered on itself. The wall is up 250 feet long, up to 250 feet high, and up to 50 feet thick.

When the wall appears, all other creatures within its area must each make a DC 24 Strength saving throw. A creature takes 33 (6d10) bludgeoning damage on failed save, or half as much damage on a successful one.

At the start of each of SCP-3000’s turns after the wall appears, the wall, along with any other creatures in it, moves 50 feet away from SCP-3000. Any Huge or smaller creature inside the wall or whose space the wall enters when it moves must succeed on a DC 24 Strength saving throw or take 27 (5d10) bludgeoning damage. A creature takes this damage no more than once on a turn. At the end of each turn the wall moves, the wall’s height is reduced by 50 feet, and the damage creatures take from the wall on subsequent rounds is reduced by 1d10. When the wall reaches 0 feet in height, the effect ends.

A creature caught in the wall can move by swimming. Because of the force of the wave, though, the creature must make a successful DC 24 Strength (Athletics) check to swim at all during that turn.

SCP-3000 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. SCP-3000 regains spent legendary actions at the start of its turn.

Slam (Costs 2 Actions). SCP-3000 makes one slam attack.

Move. SCP-3000 moves up to its speed.