As two actions, you attempt to briefly partition the mind of your foe. A creature within 20 meters must succeed on a Will saving throw or a minor personality is split off their mind that is antagonistic to the main personality. The parasitic personality functions with complete autonomy from the main personality. It does not control the body physically, but it can take two actions each round that are purely mental, such as casting a spell, in the same turn that the target takes its normal actions.
The parasitic personality casts spells as if it were the target, but can only expend 1 mana when it casts spells.
The parasitic personality actively attempts to cast spells that negatively impact the target, using the most deadly to the target. You do not have control over what the parasitic personality does, though it always works against the interest of the target.
A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.