Darkmantle
Small Monstrosity, unaligned
100 XP
Special Abilities
Echolocation
The darkmantle can't use its blindsight while deafened.
False Appearance
While the darkmantle remains motionless, it is indistinguishable from a cave formation such as a stalactite or stalagmite.
Actions
Crush
Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 6 (1d6 + 3) bludgeoning damage, and the darkmantle attaches to the target. If the target is Medium or smaller and the darkmantle has advantage on the attack roll, it attaches by engulfing the target's head, and the target is also blinded and unable to breathe while the darkmantle is attached in this way.
While attached to the target, the darkmantle can attack no other creature except the target but has advantage on its attack rolls. The darkmantle's speed also becomes 0, it can't benefit from any bonus to its speed, and it moves with the target.
A creature can detach the darkmantle by making a successful DC 13 Strength check as an action. On its turn, the darkmantle can detach itself from the target by using 5 feet of movement.
Darkness Aura (1/day)
A 15-foot radius of magical darkness extends out from the darkmantle, moves with it, and spreads around corners. The darkness lasts as long as the darkmantle maintains concentration, up to 10 minutes (as if concentrating on a spell). Darkvision can't penetrate this darkness, and no natural light can illuminate it. If any of the darkness overlaps with an area of light created by a spell of 2nd level or lower, the spell creating the light is dispelled.
Quick Reference
Running This Encounter
Darkmantles are ambush predators that excel at disorienting foes through darkness and surprise attacks. Their low AC and moderate HP make them fragile individually, but they shine when used in groups or when they catch unprepared parties. Run them as hit-and-run threats that dart in, attack, and retreat to shadows rather than standing toe-to-toe. Their blindness ability transforms the battlefield, making them tactically interesting despite their simplicity.
Combat Tactics
Darkmantles open combat by using their Darkness ability to blind and disorient enemies, gaining advantage on attacks while blinded foes suffer disadvantage. They then swoop in with melee attacks, favoring targets that appear isolated or already damaged. If seriously threatened, they attempt to fly away and hide, relying on superior mobility and aerial advantage to reposition for subsequent attacks.
Environment & Setting
Darkmantles thrive in underground caverns, deep dungeons, and dark forests with vertical terrain like cave ceilings and dense canopy cover. They favor cluttered environments with pillars, ledges, or hanging obstacles that provide concealment and allow hit-and-run tactics.