Negate healing is a cleric channel divinity power introduced in Unearthed Arcana: Ignorance is Blessed. It is meant as a substitute for divine fortune. As an Unearthed Arcana resource, it might not necessarily be canon, and may need to be discussed by the DM first. [Dr398:UA] This power has not been rated in the character optimization guides, but it's not a useful power because it is situational to the rare enemy that heals themself.