Bloop

(Special trait) healing steal: when an enemy of the Bloop attempts to heal another person, the Bloop redirects the spell to himself, giving himself temp hp on top of his own if he is at full health. This can be done as an ability and does not use a spell slot.

he has a total of 10 spell slots, with no spell being a specific level.

Spellcasting.
(cantrip) water spit: the Bloop spits a giant ball of water at an enemy, dealing 10d6 cold damage and giving them a disadvantage on their next turn.

(spell) sun laser: the Bloop channels energy from the sun and shoots a laser beam from each of its eyes and mouth, the lasers can be redirected to different enemies, dealing 7d8 fire damage each.

(spell) bubble trap: choose an enemy, the victim is trapped in a bubble and must make a Dexterity saving throw (must beat 18). every round on the Bloops turn, the drop floats up 20 ft, and when the victim succeeds the check, he falls and takes 1d6 bludgeoning damage for every 10 ft.

Action Name. swallow

swallow an enemy, this can only be done once. the victim makes a saving throw (dex) on their next two turns to escape. If both fail, the Bloop swallows them whole and they can only escape or do an action once it has been defeated

(Bonus action) unconstructive criticism: the blobfish chooses a victim and insults them telepathically. the victim is put down by its mean comment and has a disadvantage on their next 2 turns.

(reaction spell) I disagree: if the Bloop is attacked with a killing blow, he can make the enemy reroll their attack, using a completely different action while having a double disadvantage. (this can only be done once).

Enter the description of how legendary actions work for your monster here.

Time to improvise (Costs 2 Actions). the Bloop must use 2 actions to prepare this action. when prepared, the Bloop chooses to steal either: all weapons, or all spell slots from all party members. the Bloop opens its mouth and sucks in all of the chosen things. anyone swallowed previously takes the combined damage of all melee weapons if weapons are chosen, or no damage if spell slots are chosen.