Reckless. At the start of its turn, the berserker can gain advantage on all melee weapon attack rolls during that turn, but attack rolls against it have advantage until the start of its next turn.
Bestial rage. On command from its master, the thrall transforms for 1 minute in its role as a berserker. For this time, the thrall manifests a natural weapon - it counts as a simple melee weapon. 3 options are below. It might be a different weapon each time.
Bite. The thrall's mouth transforms into a bestial muzzle or great mandibles. It deals 1d8 piercing damage on a hit. Once on each of its turns when it damages a creature with this bite, it regains a number of hit points equal to double its proficiency bonus, provided it has less than half its hit points when it hits.
Claws. Each of its hands transforms into a claw, which it can use as a weapon if it’s empty. It deals 1d6 slashing damage on a hit. Once on each of its turns when it attacks with a claw using the Attack action, it can make one additional claw attack as part of the same action.
Tail. The thrall grow a lashing, spiny tail, which deals 1d8 piercing damage on a hit and has the reach property. If a creature it can see within 10 feet hits it with an attack roll, it can use its reaction to swipe its tail and roll a d8, applying a bonus to its AC equal to the number rolled, potentially causing the attack to miss.
Scimitar. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 3) slashing damage.
Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage. On hit, gain +4 hit points once each turn (if under half hit points)
Claws. 2 attacks. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 3) slashing damage.
Tail. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 7 (1d8 + 3) piercing damage.
Tail. If a tail is present: If a creature it can see within 10 feet hits it with an attack roll, it can use its reaction to swipe its tail and roll a d8, applying a bonus to its AC equal to the number rolled, potentially causing the attack to miss.
Description
Bestial thralls are one possible product of compacts or arcane oaths with fey, hags or similar that have been broken. They serve their master in a mundane capacity with the base stats block of Commoners or other suitable archetypes. When commanded by their master they enter a bestial rage, acquiring one beast part and fighting as a berserkers.
Depending on the nature of the broken pact or the curse incurred, it is possible Remove Curse will suppress this spell and allow the enslaved party to talk or act freely for a time, and Greater Restoration may allow this for up to a month. Otherwise a Wish or some other specific path is needed to free a thrall.