Ancient Snake of the Forgotten

Slither. If the Ancient Snake of the Forgotten hasn’t eaten a Huge creature in the last 24 hours, it can move through a space as narrow as 10 feet wide without squeezing, or 5 feet while squeezing.

Regeneration: The Ancient Snake of the Forgotten regains 35 hit points at the start of its turn. If the Ancient Snake of the Forgotten takes cold damage or the pool has been clean from the poison, this trait doesn't function at the start of the troll's next turn. The Ancient Snake of the Forgotten dies only if it starts its turn with 0 hit points and doesn't regenerate.

Siege Monster. The Ancient Snake of the Forgotten deals double damage to objects and structures.

Legendary Resistance (3/day). If the Ancient Snake of the Forgotten fails a saving throw, it can choose to succeed instead.

Multiattack. The Ancient Snake of the Forgotten makes two bite attacks and one constrict attack.

Bite. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) piercing damage. If the target gets hit it must succeed a DC 18 Constitution saving throw or gets the Poisoned condiotion. If the target is a Huge or smaller creature, it must succeed on a DC 16 Dexterity saving throw or be swallowed by the Ancient Snake of the Forgotten. A swallowed creature is blinded and restrained, has total cover against attacks and other effects outside the snake, and takes 21 (6d6) acid damage at the start of each of the Ancient Snake of the Forgotten’s turns. If the Ancient Snake of the Forgotten takes 40 damage or more on a single turn from a creature inside it, the Ancient Snake of the Forgotten must succeed on a DC 15 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the titanoboa. If the Ancient Snake of the Forgotten dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.

Constrict. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 27 (3d12 + 8) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained, and the Ancient Snake of the Forgotten can’t constrict another target.

Frightful Presence. Each creature of the Ancient Snake of the Forgotten’s choice that is within 120 feet of the Ancient Snake of the Forgotten and aware of it must succeed on a DC 18 Wisdom saving throw or become frightened for 1 minute. A frightened creature repeats the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the Ancient Snake of the Forgotten’ Frightful Presence for the next 24 hours.

The Ancient Snake of the Forgotten 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 Ancient Snake of the Forgotten regains spent legendary actions at the start of its turn.

Bite: The Ancient Snake of the Forgotten can make one Bite Attack

Towering Presents: The Ancient Snake of the Forgotten gets up with from the half of her Body showing of her enormice size and uses Frightful Presence. 

Sparkling Scales (costs 2 Actions) The Ancient Snake of the Forgotten’s scales refract light in iridescent cascades that are hypnotic to gaze upon. If the Ancient Snake of the Forgotten is in bright light, a creature within 30 feet that looks at it must make a successful DC 17 Wisdom saving throw or be stunned until the end of its next turn. Unless surprised, a creature can avoid the saving throw by choosing to avert its eyes at the start of its turn. A creature that averts its eyes can’t see the Ancient Snake of the Forgotten until the start of its next turn, when it can choose to avert its eyes again. If the creature looks at the Ancient Snake of the Forgotten in the meantime, it must immediately make the saving throw.