When we read incels' topics sometimes we need an "incel vocabulary" knowledge.
There is a word "copium". Copium
is a genus of lace bugs in the family "Tingidae". But the incels' meaning of "copium" isn't that. It comes from "cope" + "opium".
It is a metaphorical opiate inhaled when faced with loss, failure or defeat. The incels use it to explain or to show some of them (or some of the noncels) who is over-coping.