Monster Manual, page 154
Innate Spellcasting. The giant's innate spellcasting ability is Charisma. It can innately cast the following spells, requiring no material components: At will: detect magic, fog cloud, light 3/day each: feather fall, fly, misty step, telekinesis 1/day each: control weather, gaseous form Keen Smell. The giant has advantage on Wisdom (Perception) checks that rely on smell.
Multiattack. The giant makes two morningstar attacks.
Morningstar. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) piercing damage.
Rock. Ranged Weapon Attack: +12 to hit, range 60/240 ft., one target. Hit: 30 (4d10 + 8) bludgeoning damage.
Variant: New Giant Options
Some adult cloud giants have the magical ability to create barriers of gale-force wind around themselves that can deflect incoming missiles. Others like to fling enemies through the air. These abilities are represented by the following action options.
Fling. The giant tries to throw a Small or Medium creature within 10 feet of it. The target must succeed on a DC 20 Dexterity saving throw or be hurled up to 60 feet horizontally in a direction of the giant's choice and land prone, taking 4 (1d8) bludgeoning damage for every 10 feet it was thrown.
Wind Aura. A magical aura of wind surrounds the giant. The aura is a 10-foot-radius sphere that lasts as long as the giant maintains concentration on it (as if concentrating on a spell). While the aura is in effect, the giant gains a +2 bonus to its AC against ranged weapon attacks, and all open flames within the aura are extinguished unless they are magical.
Source: SKT, page 245
Mountain