Olhydra

Olhydra's slam attacks are treated as magical for the purpose of bypassing resistance and immunity to nonmagical attacks.

If Olhydra fails a saving throw, she can choose to succeed instead.

3/DAY

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

Olhydra can enter a hostile creature's space and stop there. She can move through a space as narrow as 1 inch wide without squeezing.

Olhydra's innate spellcasting ability is Charisma (spell save DC 20, +12 to hit with spell attacks). She can innately cast the following spells, requiring no material components:

• At will: wall of ice
• 1/day: storm of vengeance
• 3/day: ice storm

Olhydra makes two slam attacks or two water jet attacks.

Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 21 (3d10 + 5) bludgeoning damage, and the target is grappled (escape DC 19).

Olhydra can grapple up to four targets. When Olhydra moves, all creatures she is grappling move with her.

Ranged Weapon Attack: +12 to hit, range 120 ft., one target. Hit: 21 (6d6) bludgeoning damage, and the target is knocked prone if it fails a DC 19 Strength saving throw.

Olhydra summons up to three water elemental and loses 30 hit points for each elemental she summons. Summoned elementals have maximum hit points, appear within 100 feet of Olhydra, and disappear if Olhydra is reduced to 0 hit points.

1/DAY

Olhydra 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. Olhydra regains spent legendary actions at the start of its turn.

3/TURN

One creature that Olhydra is grappling is crushed for 21 (3d10 + 5) bludgeoning damage.

Olhydra releases one creature she is grappling by flinging the creature up to 60 feet away from her, in a direction of her choice. If the flung creature comes into contact with a solid surface, such as a wall or floor, the creature takes 1d6 bludgeoning damage for every 10 feet it was flung.

Olhydra transforms her watery body into acid. This effect lasts until Olhydra's next turn. Any creature that comes into contact with Olhydra or hits her with a melee attack while standing within 5 feet of her takes 11 (2d10) acid damage. Any creature grappled by Olhydra takes 22 (4d10) acid damage at the start of its turn.

Olhydra can command the waters around herself to take lair actions on the Elemental Plane of Water, or in any elemental water node (such as the Plunging Torrents, described in chapter 5). On initiative count 20 (losing initiative ties), Olhydra uses her lair action to cause one of the following effects:

• Pools of water in the lair surge outward in a grasping tide. Any creature within 20 feet of such a pool must succeed on a DC 20 Strength saving throw or be pulled up to 20 feet into the water and knocked prone.

• Water within 120 feet of Olhydra becomes murky and opaque until initiative count 20 of the next round. A creature with darkvision can't see through the water, and light can't illuminate it.

• A freezing fog fills a 40-foot-radius sphere within 120 feet of Olhydra, lasting until initiative count 20 of the next round. Creatures and objects within or beyond the fog are heavily obscured. A creature that enters the freezing cloud for the first time on a turn or starts its turn there takes 10 (3d6) cold damage.

Olhydra's presence in an elemental node creates a number of widespread effects—bad weather, strong tides, and increasing aggression from dangerous sea life.

• Violent downpours become frequent within 10 miles of the lair. A downpour occurs once every 2d12 hours, and lasts 1d3 hours. Downpours are so heavy that creatures moving overland travel at half normal speed

• Within 5 miles of the lair, currents and tides are exceptionally strong and treacherous. Any ability checks made to safely navigate or control a vessel moving through these waters has disadvantage.

• Aquatic creatures that have an Intelligence score of 2 or lower within 1 mile of the lair must succeed on a DC 15 Wisdom saving throw when they enter the area. If the saving throw succeeds, the creature is frightened and attempts to leave the area, remaining frightened while within it. On a failure, the creature becomes highly aggressive and remains in the area for 24 hours. While in this state, the creature gains advantage on saving throws against charm and fear effects.

• Natural springs and pools within 1 mile of the lair form intermittent portals to the Elemental Plane of Water, allowing elemental creatures into the mortal world to dwell near those points.

If Olhydra is destroyed or banished back to her home plane, the regional effects fade over the next 1d10 days.