Donk is a spell introduced in Dragon Quest Monsters: Joker 2. When cast, it reduces an enemy's HP by a fixed amount. Resistance to this spell is based on accuracy, rather than damage mitigation. It's successor, Kadonk, affects a wider range of enemies.
The spell itself first appeared in Dragon Quest: Dai no Daibouken, however, in the manga, the spell itself was gravity-based and creates a high-pressure gravity field to attack the opponent.
Donk makes its main series debut as an enemy exclusive spell. It costs 18 MP to cast, and will deal 75% of a character's maximum HP as damage.
Donk is learned through the Cursader, Muspell, Diabolist, Rigor Mortex, Bjorn, and Ruin skill sets and costs 12 MP to cast. It affects one group of enemies, and deals 25% of the target's current HP. As such, the spell will deal immense damage if a target is at full health, and inflict paltry wounds if they are already weakened.
Donk requires 2 MP to cast, but now only reduces the target's HP by 1/8th.