Priest · Shadow Magic · tier 1 · from level 10

Spirit Tap

Rank 5/5

Gives you a 100% chance to increase your Spirit by 100% for 15 sec after killing a non-trivial target or when an enemy afflicted by your Vampiric Embrace dies. For the duration, 50% of your Mana regeneration will continue while casting.

Doesn't change the damage or healing of any Priest spell.

Plan a Priest build

Averages, counting crits and misses, for a level 60 Priest with a typical weapon and no other gear or buffs, against a target your level. Worked out from the game's own data, the same way as the Foresight addon.