Strike Challenge

You only need to hit a lot of rats with the cog wheel, to really do it easily we will sit at the lever you hit to start the event.
Wait for a bunch to group up, usually i did it at the start of a wave, then throw once a lot of clan rats/slave rats group on the stairs (done on cata with bots during fourth wave)
there are four waves to the mid event, with the fourth having the most units. first wave has shield sv, second wave has sv, third wave has monks and few sv, fourth wave has more sv.

Other things you can do is playing on the highest difficulty you are comfortable soloing briefly, taking an absurdly tanky character like zealot or ib, killing bots and then letting as many waves stack up as possible then throwing it. there would be disabler spawns so youd have to be careful, ideally you would have cog at the top, kite in the middle until a large group is there, then make your way to the top where cog is and throw it down the stairs
https://www.youtube.com/watch?v=QNAswLphkKU