Siege Monster. The Umbravore deals double damage against structures and buildings.

Otherworldly Armor. The Umbravore's natural armor leaves it immune to bludgeoning, piercing, and slashing made by nonmagical attacks.

Dark Regeneration. The Umbravore regenerates (1d20 + 20) HP.

Visage of Terror. Looking upon the Umbravore fills a person with terror. A creature that looks at the Umbravore must succeed a DC 20 Wisdom saving throw or receive the Frightened condition. They can repeat this save every hour. If a creature succeeds the saving throw, they cannot be Frightened in this way for the next 24 hours.

Light Stealer. Any light not darkness within 60 ft. of the Umbravore becomes darkness. Any light 30 ft. after the 60 ft. is dim light.

Soul Eclipse. Viewing the Umbravore for more than one-minute results in hallucinations and memory loss determined by the DM.

Planar Bonds. The Umbravore can travel dimensions as it pleases, preferring the Material plane, but it is stuck in the Astral Plane until one specific day when the Astral Plane's hold is weakest. This date is determined by the DM but is commonly whatever Hallow's eve is in the world.

Multiattack. The Umbravore can make two Slam attacks, and one Stomp attack.

Slam. Melee Attack: +12 to hit, reach 20 ft., 1 target. Hit: 17 (2d8 + 12) bludgeoning damage.

Stomp. Melee Attack:  +12 to hit reach 5 ft., 1 target. Hit: 23 (2d10 + 12) bludgeoning damage.

Vison of the End (Recharge 5-6). Special Attack: Any creature currently looking at the Umbravore must make a DC 18 Wisdom saving throw. On failure one of the following effects can be rolled for or chosen by the DM:
(1d4)

1. The creature hears the deafening screams of the future and suffers 17 (1d12 + 9) thunder damage.
2. The creature sees into the future at the current end of the world and suffers 17 (1d12 + 9) psychic damage.
3. The creature looks into the past at the forming of the world. This creature suffers the blinded condition for the next hour or until restored.
4. The creature looks into the void of the world gone. This creature suffers the blinded condition for the next hour or until restored.

Legendary Resistance (3/Day). If the Umbravore fails a saving throw, it can choose to succeed instead.

Mythic Actions. The Umbravore has 5 Mythic actions and can use one on initiative count 20, 15, 10, 5, and 0. It cannot do the same Mythic Action twice in a row.

Slam (Costs 1 Action). The Umbravore makes a Slam attack.

Stomp (Costs 1 Action). The Umbravore Makes a Stomp attack.

Reform (Costs 3 Actions). The Umbravore regenerates (1d20 + 20) HP.

Recharge (Costs 2 Actions). If it can the Umbravore can attempt to recharge its Vision of the End attack. It does not use the attack.