Stroke of Genius (Slinger)

Achievement Unlocked: Stroke of Genius Skill Unlocked: Siphon Your intellectual capabilities will not improve much from further mental stat improvements. Intellect increases your mana reservoir slightly more per point, applies retroactively

Siphon, Active Skill, Level 1 By targeting one willing entity within (Skill Level) meters, you may drain or give the target mana at an efficiency rate of 50+(Skill Level x 10)%. If your mana pool is filled beyond capacity as a result of this effect, excess mana is lost at a rate of 10^(Seconds Passed/15) mana per second.

Reference
Unlocked in Chapter 160 "Dear McCracken"