Reduces the mana cost of your Scorch spell by 50%/100%.
Improved Scorch is a magetalent reduces the mana cost of Scorch by up to 100%. This talent allows a mage to remain useful even after they have run out of mana. When combined with Hot Streak and Improved Hot Streak, reasons for using this spell become very clear.
Patch 3.3.0 (2009-12-08): The debuff from this talent no longer stacks, and instead can apply the full effect from a single cast of [Scorch].
Hotfix (2009-04-21): "Shadow Mastery and Improved Scorch will no longer stack with each other."
Patch 3.0.2 (2008-10-14): Increased spell critical strike chance against the affected target.
Old - increased fire damage done to the target by 3% per stack.
Patch 1.4.0 (2005-05-05): Redesign. Scorch spells have a 20/40/60/80/100% chance to cause your target to be vulnerable to Fire damage. This vulnerability increases the Fire damage dealt to your target by 2% and can be stacked up to 5 times for a total of 10% increased Fire damage.
Edit
Patch 3.3.0 (2009-12-08): The debuff from this talent no longer stacks, and instead can apply the full effect from a single cast of [Scorch]. 
Hotfix (2009-04-21): "Shadow Mastery and Improved Scorch will no longer stack with each other." 
