Ossuvine, the Thousand-Year Bloom

Traits

• Legendary Resistance (3/Day). If Ossuvine fails a saving throw, it can choose to succeed instead. Each time it does, one of its petals closes and does not open again for a year.
• Rooted Eternal. Ossuvine cannot be moved, teleported or banished while any part of its root mass remains in the valley. Spells and effects that would relocate it instead deal 55 (10d10) force damage to it.
• Memory Pollen. A creature that ends its turn within 60 feet of Ossuvine must succeed on a DC 25 Wisdom saving throw or lose one memory of its own choosing, selected by the DM if the player will not choose. The memory is not destroyed; it is filed, and Ossuvine can recite it.
• Regeneration. Ossuvine regains 30 hit points at the start of its turn. If it takes fire damage, this trait does not function at the start of its next turn. Ossuvine dies only if it starts its turn with 0 hit points and does not regenerate.
• Siege Monster. Ossuvine deals double damage to objects and structures, and the roots do the work whether or not it is paying attention.

Spellcasting

Their spellcasting ability is Wisdom (spell save DC 24, +16 to hit with spell attacks).

• At will. Detect Magic, Druidcraft
• 2/day each. Detect Thoughts (2nd level), Dominate Person (5th level), Modify Memory (5th level), Speak with Plants (3rd level)

Actions

• Multiattack. Ossuvine makes four attacks: three Bough attacks and one Root Spear attack.
• Bough. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 35 (4d12 + 9) bludgeoning damage. A limb of black heartwood, thicker than a cart. If the target is Large or smaller it is also grappled (escape DC 25), and Ossuvine can hold up to four creatures this way.
• Root Spear. Melee Weapon Attack: +17 to hit, reach 60 ft., one target. Hit: 31 (4d10 + 9) piercing damage. A root breaks the ground beneath a creature Ossuvine can sense. The target cannot be moved from the space it occupies until the root is severed (AC 21, 40 hit points, immunity to poison and psychic damage).
• Thousand-Year Bloom (Recharge 6). Ossuvine opens. For one round every living thing within 120 feet sees the valley as it was a thousand years ago, including the people who were in it. Each creature in the area must make a DC 25 Wisdom saving throw, taking 110 (20d10) psychic damage on a failed save, or half as much damage on a successful one.

Bonus Actions

• Seedfall. A pod bursts above a point Ossuvine can sense within 120 feet. The ground in a 15-foot radius becomes difficult terrain as seedlings take root, and a creature that starts its turn there takes 11 (2d10) piercing damage. The seedlings wither after one minute unless Ossuvine feeds them.

Reactions

• Graft. Trigger: A creature grappled by Ossuvine drops to 0 hit points. Roots close over the body. The creature cannot be revived by any means short of a wish spell, and one flower on Ossuvine’s crown opens in its face. Party members who look at that flower recognise it.

Legendary Actions

Ossuvine, the Thousand-Year Bloom 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. Ossuvine regains spent legendary actions at the start of their turn.

• Bough Attack. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 35 (4d12 + 9) bludgeoning damage. A limb of black heartwood, thicker than a cart. If the target is Large or smaller it is also grappled (escape DC 25), and Ossuvine can hold up to four creatures this way.
• Recite. Ossuvine speaks aloud a memory it has taken. One creature that can hear it must succeed on a DC 25 Wisdom saving throw or be incapacitated until the end of its next turn. A creature whose own memory is recited has disadvantage on this save.
• Root Surge (Costs 2 Actions). The valley floor heaves. Each creature on the ground within 60 feet of Ossuvine must succeed on a DC 25 Dexterity saving throw or take 27 (5d10) bludgeoning damage and be moved 20 feet toward the trunk.

Lair Actions

• The Valley Remembers. Figures of packed pollen walk out of the treeline and go about a day’s work that ended a thousand years ago. Each creature that can see them must succeed on a DC 25 Wisdom saving throw or spend its action watching. A creature that takes damage may repeat the save at the end of its turn. (Anywhere in the valley)
• Deep Root. The soil in a 40-foot-radius area becomes as soft as meltwater. Each creature there must succeed on a DC 25 Strength saving throw or sink to its waist and be restrained until it escapes with a DC 25 Strength check.

Regional Effects

• The Valley Does Not Age. Plants within the region do not go to seed and animals do not bear young. Nothing rots. Travellers who camp a single night wake rested but cannot recall what they were travelling toward until they leave. The effect extends 3 miles from the lair.
• Borrowed Names. Anyone who has spent more than a tenday in the region begins answering to a name that is not theirs, and is confused but not troubled when this is pointed out. The effect ends a month after they leave. The effect extends 3 miles from the lair.