the long story short of mithrix and providence in risk of rain 2 is that providence liked living and sapient creatures that were “potential risks” due to their unpredictability and mithrix liked servile constructs like robots and such
the two of them are brothers and they grew distant due to their differences in creation, with mithrix essentially policing providence because again sapient living things with soul were a risk
the two of them also can’t go into space because it makes them sick somehow so mithrix at one point presents a proof of concept of a teleporter that can get them to the moon to his brother and providence asks him to go through first
mithrix obliges and tries to meet him in the middle in that sense and then providence deactivates it from the planet side and mithrix is then trapped on the moon
this causes mithrix to understandbly get upset with providence and gives providence free reign to do what he wants with the planet which is to relocate (somehow? maybe he recreated them) doomed species to the planet as a sort of nature reserve
mithrix sees said doomed species as vermin at best and creatures that deserved their own extinction at worst
this is all brought to a rather unsatisfying end when in RoR1 providence is killed by the survivors after the ship crash landed on the planet, and in RoR2 the rescue party kills mithrix
depressingly enough mithrix’s final lines after you kill him are usually something to do with his brother and occasionally how they messed up
