Corrupted Bullywug

Amphibious. The corrupted bullywug can breathe air and water.

Standing Leap. The corrupted bullywug's long jump is up to 20 feet, and its high jump is up to 10 feet, with or without a running start.

Unknowable Mind. It is impossible to determine the thoughts of a corrupted creature, and the creature has advantage to resist mind-affecting abilities. The creature randomly decides how to attack, and attacks any non-corrupted creature in range at complete random.

Spread Corruption. Once per week the corrupted bullywug can attempt to spread the corruption with its bite attack. It does so with the first bite that lands on any creature while it is able to use this ability. Target creature makes a constitution saving throw (dc 8) to resist the effect. If the target has more hit dice than the corrupted bullywug, then they roll with advantage.
If a creature fails this save, they feel a compulsion to move towards the source of the corruption (typically a dark mage of some variety). The afflicted creature makes a wisdom save (dc 10) with disadvantage, or immediately begins walking in the direction of the source of corruption (whether they know the location or not). They make the save once every hour until they arrive at the source, however two successful wisdom saves in a row will clear the effect completely.

Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 3 (1d4 + 2) [bludgeoning] damage.

Claw. Melee Weapon Attack: +3 to hit, reach 5 ft., one target, Hit: 3 (2d4) [slashing] damage.