Fire Aegis. A creature that touches the giant or hits it with a melee attack while within 10 feet of it takes 11 (2d10) fire damage.

Spellcasting. The giant is a 15th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). It knows the following sorcerer spells:

Cantrips (at will): control flames, create bonfire, fire bolt, light, mage hand, prestidigitation
1st level (4 slots): burning hands, fog cloud
2nd level (3 slots): cannon blast (new), pyrotechnics
3rd level (3 slots): fireball, stinking cloud
4th level (3 slots): heat wave (new), wall of fire
5th level (2 slots): immolation, molten upheaval (new) 
6th level (1 slot): investiture of flame
7th level (1 slot): delayed blast fireball
8th level (1 slot): incendiary cloud, wall of lava (new)

Gigantic Pyromancy. When the giant casts a pyromancy spell or a spell that deals fire damage, it treats the spell's range along with each length, range, and radius within the spell's description as if it were doubled in length, and it adds its Charisma modifier (+4) to all the damage rolls of that spell.

Sorcery Points. The giant has 15 sorcery points. It can spend sorcery points when it casts a spell to gain one of the following benefits:

   Heightened Spell: The giant spends 3 sorcery points to give one target of the spell disadvantage on its first saving throw made against the spell. 
   Quickened Spell: The giant spends 2 sorcery points to change the casting time of the spell to 1 bonus action for this casting. 
   Twinned Spell: The giant can spend a number of sorcery points equal to the spell's level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip). To be eligible for Twinned Spell, a spell must be incapable of targeting more than one creature at the spell's current level.

War Caster. The giant has advantage on Constitution saving throws that it makes to maintain its concentration on a spell when it takes damage. It also can perform the somatic components of spells even when it has weapons or a shield in one or both hands.

Multiattack. The giant makes two forge hammer attacks.

Forge Maul. Melee Weapon Attack: +13 to hit, reach 10ft., one target. Hit: 28 (6d6 + 7) bludgeoning damage plus 10 (3d6) fire damage.

Molten Rock. Ranged Weapon Attack: +13 to hit, range 60/240 ft., one target. Hit: 29 (4d10 + 7) bludgeoning damage plus 21 (6d6) fire damage.