Eternatus (5e Creature)
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Gargantuan dragon (titan), neutral
Saving Throws Dex +13, Con +16, Wis +13
Legendary Resistance (3/day). If Eternatus fails a saving throw, it can choose to succeed instead.
Magic Resistance. Eternatus has advantage on saving throws against spells and other magical effects.
Pressure. All creatures of Eternatus's choice within 60 feet of it have disadvantage on Constitution saving throws.
Unnerve. All creatures of Eternatus's choice within 60 feet of it have disadvantage on Wisdom saving throws.
Magic Weapons. Eternatus's weapon attacks are magical.
Multiattack. Eternatus makes three attacks: one with its Spines, one with its Tail, and one with its Dynamax Cannon. Eternamax Eternatus additionally uses Eternabeam if it can.
Eternamax. Eternatus magically transforms into Eternamax Eternatus. Its statistics are the same in each form. This transformation lasts for 1 hour, until Eternatus becomes unconscious, or until Eternatus dismisses it as an action.
Spines. Melee Weapon Attack: +16 to hit, reach 15 ft., one target. Hit: 33 (4d12 + 7) piercing damage.
Tail. Melee Weapon Attack: +16 to hit, reach 25 ft., one target. Hit: 25 (4d8 + 7) bludgeoning damage. If the target is a creature, it must succeed on a DC 24 Strength saving throw or be knocked prone.
Dynamax Cannon. Ranged Spell Attack: +16 to hit, range 100/400 ft., one target. Hit: 51 (8d10 + 7) force damage.
Eternabeam (Eternamax only, Recharge 6). Eternamax Eternatus releases a beam of destructive energy in a 100-foot by 20-foot line in front of it. All creatures of Eternatus's choice in that area must succeed on a DC 24 Dexterity saving throw. On a failure, a creature takes 54 (12d8) force damage and must succeed on a DC 24 Charisma saving throw or be reduced for 1 minute. Its size is halved in all dimensions, and its weight is reduced to one-eighth of normal. This reduction decreases its size by one category—from Medium to Small, for example. While reduced in this way, it also has disadvantage on Strength checks and Strength saving throws. The target's weapons also shrink to match its new size. While these weapons are reduced, the target's attacks with them deal 1d4 less damage (this can't reduce the damage below 1). A creature can repeat the saving throw at the end of each of its turns, ending the effect on a success. On a successful save, a creature takes half as much damage but isn't otherwise affected.
Eternatus 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. Eternatus regains spent legendary actions at the start of its turn.
Attack. Eternatus makes one spines attacks or one tail attack.
Move. Eternatus moves up to half its speed.
Cosmic Power (Costs 2 Actions). Eternatus gains resistance to two damage types of its choice until the start of its next turn.