Xanka

When the xanka is hit by a melee weapon and the final, adjusted attack roll is 19 or less, the weapon gains a permanent -1 penalty to damage rolls, after inflicting damage for this attack. If the penalty reaches -5, the weapon is destroyed. Even magic weapons are subject to this effect.

The xanka's weapon attacks are magical.

A xanka doesn't require air, food, drink, or sleep.

Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) force damage, and the xanka regains hit points equal to the damage caused by its attack.

In addition, a living creature hit by this attack must make a successful DC 12 Dexterity saving throw or suffer a gaping wound that causes 2 (1d4) necrotic damage at the end of each of the creature's turns until the wound is treated with magical healing or with a successful DC 10 Intelligence (Medicine) check. If a creature who fails this saving throw is wearing armor or using a shield, the creature can choose to prevent the necrotic damage by permanently reducing the AC of its armor or shield by 1 instead.