III. Mana Regeneration: Rapture (3.3.5)
Rapture is an important part of the mana regeneration for a discipline priest. What it does is return 2.5% of your total mana each time one of your shields is fully absorbed.
The details are a bit more complex, though. Rapture can proc only once every 12s. However, if multiple shields break at exactly the same time and Rapture is not on cooldown, Rapture will proc for most (usually all) of the shields.
There are encounters where you can actively increase your chances for multiple procs. One popular example is the Lich King encounter. Shields are the ideal way to counter the Infest ability, there. However, it does make sense to not shield the tanks (except for emergencies, of course). If you shield the tanks, chances are high Rapture is on internal cooldown when Infest pops the rest of your shields, so you cannot profit from multiple rapture procs. Depending on gear, aura strength and raid type, you may need to downrank your shields for Infest, though. In 10 man normal, Infest doesn't hit hard enough to pop max rank shields from most priests.
