Death Burst. When the giant dies, it explodes in a burst of flame. Each creature within 30 ft. of it must make a DC 20 Dexterity saving throw, taking 22 (4d10) fire damage on a failed save, or half as much damage on a successful one.

Heated Weapons. Any metal melee weapon the giant wields deals an extra 5 (1d10) fire damage on a hit (included in the attack).

Innate Spellcasting. The giant's innate spellcasting ability is Wisdom (spell save DC 17, +9 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

Multiattack. The giant makes two greatsword attacks.

Greatsword. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 28 (6d6 + 7) slashing damage plus 5 (1d10) fire damage.

Mote of Flame. Ranged Spell Attack: +9 to hit, reach 120 ft., one target. Hit: 17 (2d12 + 4) fire damage. 

Rock. Ranged Weapon Attack: +12 to hit, range 60/240 ft., one target. Hit: 29 (4d10 + 7) bludgeoning damage.

The fire titan can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The giant regains spent legendary actions at the start of its turn.

Detect. The giant makes a Wisdom (Perception) check.
Mote of Flame Attack. The giant makes a mote of flame attack.
Blazing Teleport. The giant magically teleports, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied space it can see. After it teleports, each creature within 30 feet of the giant must make a DC 17 Dexterity saving throw, taking 13 (2d12) fire damage on a failed save, or half as much on a successful one.