Tried out the shadow mundus stone and it seems to be working. I saw a definite increase in my critical strike damage versus not having any mundus stone effects.
Would this be worth using now over the thief stone, if you already have around 50% crit (spell or physical)?
Worstluck - Breton Nightblade "Some of us refused to bow. We knew the old ways would lead us back to having a kingdom of our own."
―Madanach
Elfluck - Dunmer Dragonknight "When I will walk the earth again, the Faithful among you shall receive your reward: to be set above all other mortals forever. As for the rest: the weak shall be winnowed: the timid shall be cast down: the mighty shall tremble at my feet and pray for pardon."
―Mehrunes Dagon
Deadluck -Imperial Templar "Men are but flesh and blood. They know their doom, but not the hour"
―Uriel Septim
Daggerfall Covenant