EXPLANATION
In Ulduar there is a boss named General Vezax. This boss has an aura called Aura of Despair. With the recent patch, the druid skill Lifebloom is now able to return 1/4th of the initial mana cost(245) of the spell instead of the regular 1/2 (450) on the General Vezax fight. The exploit here is to drop the mana cost of Lifebloom to below the amount returned, which is effectively letting you regen mana (possibly VERY useful for hard mode).
As you can see with the previous picture, for the one Lifebloom casted, I received 244 mana back. In the picture is the tool tip I had for Lifebloom (210 mana cost).
What you can and cannot do
Things to wear for this fight in order to attain this are Spark of Hope and Two piece from T7. Standing in the Shadow Crash is also mandatory for the reduction.
During that normal mode kill of the boss, I also tested the mana cost using Lower City Prayerbook, but this does not reduce the mana cost further.
Comments
Sorry I couldn't have gotten this out sooner. Last week during the Vezax kill I found myself without my Spark of Hope or the two piece tier seven equipped, otherwise last Friday this would have been on the boards.
Hope this helps any raiding druids kill General Vezax in both normal and hard modes!