Lucifer's glare towards Furball was full of hate and contempt and the devil did not shy away from pushing towards her an endless barrage of darkness lance's , however the aiming was a mess due to all the pain that Lucifer was suffering and completely all over the place.
Medivh saw this opportunity and decided that he needed to exploit it somehow and hence unleashed the attack wheel of fire on Lucifer.
The wheel of fire was a tier 4 attack and one of the best that Medivh could summon as it was not meant for AOE type damage but rather used in one vs one combat, making it packed with energy.
However, Medivh was given a taste of reality fairly quickly when Lucifer swatted his wheel of fire like swatting off a pesky fly as his rhythm of attacking furball did not even slow down.