Rank 1 Afflicting a target with Serpent Sting allows 25% of your Mana Regeneration to continue while casting for 15 sec, increased to 50% when Rapid Killing is consumed.
Rank 2 Afflicting a target with Serpent Sting allows 50% of your Mana Regeneration to continue while casting for 15 sec, increased to 100% when Rapid Killing is consumed.