Patra (5e Creature)
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Huge swarm of Small fiends, lawful evil
Limited Magic Immunity. The swarm is immune to spells of 6th level or lower unless it wished to be affected. It has advantage on saving throws against all other spells and magical effects. Spell attack rolls targeting the swarm are made with disadvantage.
Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Small fiend. The swarm can't regain hit points or gain temporary hit points.
Weak Point. At the center of the swarm that is patra is a noticeably larger body that enhances coordination throughout the swarm. Any attack made as a called shot against this central body ignores the swarm's damage resistance. A melee attack can only hit this weak point if it can reach the center of the swarm.
Multiattack. The swarm bites four times.
Bites. Melee Weapon Attack: +10 to hit, reach 0 ft., one target in the swarm's space. Hit: 28 (8d6) piercing damage, or 14 (4d6) piercing damage if the swarm has half of its hit points or fewer.
The creature collectively known as patra (or "eyesoar") is comprised of numerous hare-sized, insect-like bodies, each of which darts around on agile wings and glares with a singular eye. This swarm of demons acts with one mind, and the numerous bodies which make up the swarm are able to effortlessly fly in intricate and rapid patterns that would be virtually impossible for separate creatures to accomplish. The bodies that occupy this swarm are akin to a school of fish, reproducing within their own numbers, but always act as one unit that never willingly separates.
Evil Servants. As a bestial demon, a patra feeds on evil the way a plant might feed on light. Any one of these swarms is drawn towards those who spread malice and destruction, and are eager to defend and obey them the way a domesticated dog might do so with a hylian. A patra is usually only found as the obedient pet of an entity both immensely powerful and evil, to include the likes of Ganon himself, or evil wizzrobe cults.