You touch the forehead of a living creature with an open palm, holding the gem in your other hand. Target must make a wisdom saving throw or take 12d10+20 necrotic damage. If the target is reduced to 0 hit points, you tear their soul into pieces and absorb some of their abilities. 

Chose one of the following:

If the target had a class, you may chose one of their abilities for every 4 levels they had achieved (rounded down)

If the target could fly, swim, climb, or burrow you gain the ability to do so (at half of its original speed)

You gain the targets damage immunities and resistances

If the target had blind sense, tremor sense or true sight you gain that ability

You gain the ability to communicate in the same way the target would

You absorb their magical ability, learning all spells they knew and gaining spell slots equal to half of their original slots (rounded down)