This one here is for tower.
If you have an ill gill getting out of control and rushing back and forth, there are 3 things you can do:
1. Run a ramp upwards because ill gills can only walk upwards and get stuck if they rush upwards.
2. interrupt the rush with normal attack first and use special after.
3. use twinblaze gifoi to create a barrier between you and the ill gill, this will stun and interrupt the rush aswell but you have to be quick with switching weps (these work against the grimm reaper aswell)