Frostfire Rex

Born from the chaotic energy of the plane of fire colliding with the plane of water, the Frostfire Rex is a legendary creature that should not be. Widely believed to be the only one of its kind, the Frostfire Rex is known for its ruthless aggression, and hunting not out of hunger but anger, particularly directed at creatures and cities that use the arcane arts.
Resembling a fifty-foot-tall and seventy-foot-long Tyrannosaurus Rex with two heads, the Frostfire Rex cackles with elemental energy. The left side of its hide and mouth drips with the lava of Ignathar, the elemental plane of fire. Its right side chilled with the frost of Aquenias, the elemental plane of water. Covered in molten and frozen spikes, the Frostfire Rex’s tail extends into an enormous and dexterous clawed hand.

Lair

The Frostfire Rex does not have a lair to call home. Instead, it appears sporadically across the Realms of Remembrance, obliterating everything in its path before disappearing as quickly as it came. Attempts have been made to track its return and provide townsfolk enough time to evacuate. Unfortunately, scholars have been unable to predict the chaotic monstrosity's wrath.

Divine Manifestation

The Frostfire Rex’s violent creation, power and hatred for arcane magic have led many to believe it is manifested with divine authority. Magic in Erenel is made available only by reaching into the bonded remains of a dead creator. Perhaps the destructive beast that can swallow all but the largest creatures in its two elemental maws exists as punishment for a selfish world.

While the Frostfire Rex rampages across whatever plane is unfortunate enough to draw its attention, denizens of Erenel hide in terror and call out to the gods for mercy.

Average Height

50 feet

Average Weight

180,000 lbs

Average Length

70 feet

Geographic Distribution

• Elemental Planes

Frostfire Rex Statblock

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Frostfire Rex 5E Statblock

Frostfire Rex CR: 26

Gargantuan monstrosity, unaligned

Armor Class: 22

Hit Points: 507 (26d20+234)

Speed: 50 ft

STR

30 +10

DEX

11 +0

CON

29 +9

INT

13 +1

WIS

15 +2

CHA

10 +0

Saving Throws: Int +9, Wis +10, Cha +8

Skills: Intimidation +8, Perception +10

Damage Immunities: cold, fire; bludgeoning, piercing, and slashing from nonmagical attacks

Condition Immunities: charmed, frightened, paralyzed, poisoned, restrained

Senses: passive Perception 18

Challenge Rating: 26

Frostfire

Cold and fire damage dealt by Frostfire Rex ignores damage resistances.

Legendary Resistance (4/Day)

If Frostfire Rex fails a saving throw, it can choose to succeed instead.

Magic Resistance

Frostfire Rex has advantage on saving throws against spells and other magical effects.

Mythic Awakening (Recharges after a Short or Long Rest)

If Frostfire Rex would be reduced to 0 hit points, it instead regains 200 hit points and gains 200 temporary hit points, it recharges its Breath Weapon, and it regains any expended uses of Legendary Resistance. If a creature hits Frostfire Rex with a melee attack while it has these temporary hit points, the creature takes 5 (1d10) cold damage and 5 (1d10) fire damage. Additionally, the Frostfire Rex can now use the options in the "Mythic Actions" section for 1 hour. Award a party an additional 90,000 XP (180,000 XP total) for defeating Frostfire Rex after its Mythic Awakening activates.

Siege Monster

Frostfire Rex deals double damage to objects and structures.

Tooth and Fang

Frostfire Rex gains one extra reaction that can be used only for opportunity attacks made with a bite attack.

Two Heads

Frostfire Rex has advantage on saving throws against being blinded, deafened, stunned, or unconscious.

Actions

Multiattack

Frostfire Rex makes three attacks: one with its frost bite, one with its lava bite and one with its tail.

Frost Bite

Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit 21 (2d10+10) piercing damage plus 13 (2d12) cold damage.

Lava Bite

Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit 21 (2d10+10) piercing damage plus 13 (2d12) fire damage.

Tail

Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit 19 (2d8+10) bludgeoning damage and the target is grappled (escape DC 26). If the target doesn't escape by the end of its next turn, Frostfire Rex throws the target up to 60 feet in a straight line. The target lands prone and takes 21 (6d6) bludgeoning damage.

Frostfire Breath (5-6)

Frostfire Rex exhales a blast of energy in a 300-foot cone. Each creature in that area must make a DC 26 Dexterity saving throw. On a failed save, the creature takes 39 (6d12) cold damage and 39 (6d12) fire damage. On a successful save, the creature takes half as much damage.

Legendary Actions

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

Move (Costs 1 Action)

The Frostfire Rex moves up to half its speed.

Tail (Costs 1 Action)

The Frostfire Rex makes one tail attack.

Elemental Eruption (Costs 3 Action)

The Frostfire Rex flares with elemental energy. Each creature in a 60-foot-radius sphere centered on the Frostfire Rex must succeed on a DC 26 Dexterity saving throw or take 14 (3d8) cold damage and 14 (3d8) fire damage.

Mythic Actions

Inhale (Costs 1 Action)

Frostfire Rex rolls to recharge its breath weapon.

Rampage (Costs 2 Actions)

Frostfire Rex makes two bite attacks: one with its frost bite and one with its lava bite.