It's one of the best this year
With the Mists of Lorien, you have a chance to pick and choose which cards you want to get rid of, or all of them if you have enough mana
Sure, you lose life in exchange, but being able to take a problematic enchantment the second it becomes a problem is a huge boost to black decks
Opening Hand 6 Without mana or a Bazaar, this hand does nothing, and is dead in the water
You need your opponent to have cast at least three spells for it to be worth the 4 mana you invest into it, which happens in a single turn cycle in Commander but takes far too long in Limited
Since it only costs 1 mana, you can get it online immediately and control the top of your deck while triggering all your death synergies