Gargantua

At the start of each of the gargantua's turns, each creature of the gargantua's choice within 30 feet of it must make a DC 19 Wisdom saving throw. On a failed save, a target sees the gargantua as a manifestation of the target's worst fears; it takes 17 (5d6) psychic damage and has the frightened condition until the start of the target's next turn. On a successful save, a target is immune to this gargantua's Weird Aura for 24 hours.

The gargantua makes two Slam or Rock attacks.

Melee Attack Roll: +15 to hit, reach 20 ft., one target. Hit: 27 (3d12 + 8) bludgeoning damage.

Ranged Attack Roll: +15 to hit, range 120/480 ft., one target. Hit: 24 (3d10 + 8) bludgeoning damage.

Immediately after the gargantua takes damage from a Large or smaller creature it can see within 20 feet of itself, it attempts to flick the creature away. The target must succeed on a DC 23 Strength saving throw, or the target takes 18 (3d6 + 8) bludgeoning damage, is pushed horizontally up to 100 feet away from the gargantua, and has the prone condition.

Immediately after a creature the gargantua can see casts a spell of 5th level or lower, the gargantua tries to copy the spell. That creature must succeed on a DC 19 Charisma saving throw, or the gargantua immediately casts the same spell at the same level (+11 to hit with spell attacks, spell save DC 19), requiring no material components and choosing the spell's targets.