Bortriess - Lothrielle's Protector

Regenerative. While Bortriess remains in saltwater, it gains 2D10 health at the start of its turn.

Magic Resistance. Bortriess has advantage on saving throws against spells and other magical effects.

Immutable Form. The colossus is immune to any spell or effect that would alter its form.

Legendary Resistance (3/Day). If Bortriess fails a saving throw, he can choose to succeed instead.

Legendary Actions (3/Round)

Sharp Points Creatures that begin their turn within 5 feet of Bortriess must make a DC 15 dexterity saving throw or take 2D6 piercing damage and 2D6 poison damage.

Legendary Swordsman When Bortriess lands an attack with their Coral Sword, they can apply any weapon mastery to the attack for 1 legendary action.

Multiattack: Bortriess uses its Whirlpool or Prismatic Breath attack if it has it, and also makes 2 Coral Weapon attacks.

• Whirlpool (Recharge 5–6). The Coral Golem creates a whirlpool in a 30-foot radius centered on a point it can see within 60 feet of it. The area becomes difficult terrain for creatures other than the Coral Golem. Each creature in the water in the area when the whirlpool is created must make a DC 14 Strength saving throw. On a failed save, a creature takes 18 (4d8) bludgeoning damage and is pulled 10 feet toward the center of the whirlpool. On a successful save, the creature takes half the damage and isn’t pulled.
• Prismatic Breath.  (Recharge 5–6) Bortriess exhales a breath of magical potent energy which effects creatures in random ways. The breath either fires in a 60 ft straight line or 30 ft cone.

1. Red. The target takes 10d6 fire damage on a failed save, or half as much damage on a successful one.
2. Orange. The target takes 10d6 acid damage on a failed save, or half as much damage on a successful one.
3. Yellow. The target takes 10d6 lightning damage on a failed save, or half as much damage on a successful one.
4. Green. The target takes 10d6 poison damage on a failed save, or half as much damage on a successful one.
5. Blue. The target takes 10d6 cold damage on a failed save, or half as much damage on a successful one.
6. Indigo. On a failed save, the target is restrained. It must then make a Constitution saving throw at the end of each of its turns. If it successfully saves three times, the spell ends. If it fails its save three times, it permanently turns to stone and is subjected to the petrified condition. The successes and failures don't need to be consecutive; keep track of both until the target collects three of a kind.
7. Violet. On a failed save, the target is blinded. It must then make a Wisdom saving throw at the start of your next turn. A successful save ends the blindness. If it fails that save, the creature is transported to another plane of existence of the GM's choosing and is no longer blinded. (Typically, a creature that is on a plane that isn't its home plane is banished home, while other creatures are usually cast into the Astral or Ethereal planes.) 
8. Special. The target is struck by two rays. Roll twice more, rerolling any 8.

• Coral Shard Barrage. Ranged Weapon Attack: +6 to hit, range 30/60 ft., one target. Hit: 27 (6d8) piercing damage. The Coral Golem can use this attack three times before running out of coral shards. To recover this ability, the Coral Golem must spend a turn not moving and taking no actions.
• Coral Sword. Melee Weapon Attack: +9 to hit, reach 10 ft., 1 target. Hit: 4D6 Slashing damage. The target makes a constitution saving throw. On a failed save, the target takes an additional 6D6 poison damage and is now poisoned. When the target is poisoned in this way, they have disadvantage on their next saving throw.
• Coral Bash. Melee Weapon Attack: +9 to hit 1 target. Hit: 2D6 Bludgeoning Damage. The target must make a strength saving throw or have their speed halved, and AC reduced by 1 until the end of Bortriess's next turn.

[Legendary] Coral Attack. Bortriess can move up to 15 feet and use any of its coral attacks.

[Legendary] Gleam. Bortriess summons a bright flash from its coral. All enemies within 90 feet of it must make a DC 18 constitution saving throw or be blinded until the end of Bortriess' next turn.

[Legendary] Chip Off. Bortriess takes 3D10 bludgeoning damage and ends one condition or spell effect on it.

Corrupted By Ran. Ran's influence triggers a revival in Bortriess, who fights for her instead. When Bortriess reaches 50 HP or less, they enter this state and regain 6D10 hit points.

Investiture of Ice. 

Until the spell ends, ice rimes your body, and you gain the following benefits:

• You are immune to cold damage and have resistance to fire damage.

• You can move across difficult terrain created by ice or snow without spending extra movement.

• The ground in a 10-foot radius around you is icy and is difficult terrain for creatures other than you. The radius moves with you.

• You can use your action to create a 15-foot cone of freezing wind extending from your outstretched hand in a direction you choose. Each creature in the cone must make a Constitution saving throw. A creature takes 4d6 cold damage on a failed save, or half as much damage on a successful one. A creature that fails its save against this effect has its speed halved until the start of your next turn.

Coral Motes: Bortriess can use its bonus action to send a coral mote at an enemy. Seven star-like motes of light appear and orbit your head until the spell ends. You can use a bonus action to send one of the motes streaking toward one creature or object within 120 feet of you. When you do so, make a ranged spell attack. On a hit, the target takes 4d12 radiant damage. Whether you hit or miss, the mote is expended. The spell ends early if you expend the last mote. If you have four or more motes remaining, they shed bright light in a 30-foot radius and dim light for an additional 30 feet. If you have one to three motes remaining, they shed dim light in a 30-foot radius.