Cunning survivor. The giant can add its wisdom modifier to its ac.

Innate Spellcasting. The giant's innate spellcasting ability is Charisma (spell save DC 17). It can innately cast the following spells, requiring no material components:

At will: detect magic, fireball, levitate, light, darkness

3/day each: control weather, summon greater demon

1/day each: giant insect  (the giant can cast this spell on any creature, if there is not a giant version of that creature then its size is increased by 1 and it gains 20 hp and 5 strength and constitution), infernal calling  (max cr 18 no components required).

Multiattack. The giant makes two greatsword attacks.

Greatsword. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 30 (6d6 + 9) slashing damage.

Rock. Ranged Weapon Attack: +14 to hit, range 60/240 ft., one target. Hit: 35 (4d12 + 9) bludgeoning damage.

Summon demon (Recharge 5–6). The giant selects one creature within 40ft of it. That creature must succeed on a dc (30-that creature’s number of hit dice) constitution saving throw on a success the giant takes 3d8 necrotic damage on a failed save that creature is reduced to zero hp and the giant summons one demon with cr equal to or less than that creature’s (use level for characters).