From Dragon Mania Legends (DML) Wiki
Damage Leech can be learned by all Ancient Dragons. It is an active offensive skill that inflicts negative status effects by reducing the amount of damage an opponent can cause and increases the caster's damage by the same amount.
The damage reduction caused by Damage Leech does not negate or reduce the effectiveness of Dark Clouds, Stone Shield, Shade of Oneself or Wisdom of the Ancients nor does it reduce damage from Vengeful Sword or Death Mark.
This skill can be used multiple times by one caster, but only the duration is prolonged.
It can be stacked by different casters targeting different opponents.
The caster reduces target's base damage by x and deals x more damage over 2 turns. Skill effectiveness is based on caster's Dragon's Attack Strength (DAS)
Reduces target damage and deals more damage by 60% DAS.