Tree Leech

You point a finger at someone and let loose a withering bolt, which strikes the target in an attempt to leech the liquid from their bodies. The target takes 5d6 necrotic damage on hit and must make a DC 18 constitution saving throw or begin to have the liquids in their flesh, provided they have it, sap from them, taking 2d8 necrotic damage at the start of their turns, as well as halving their movement speed. The target may remake the constitution saving throw at the end of each of their turns until the spell is ended, ending the spell on a success. This spell's damage increases by 1d6 on hit and 1d8 on failed save for each spell slot level above 6th level expended for this spell