It's not so hard or broken for your opponents to stop, they just need to deal with you one turn at a time
In Sultai colors, you can do some nasty things with this, from using Buried Alive/Entomb early on to setup a great later turn, to just replaying the Maha, Its Feathers Night and Toxrill, the Corrosive that your opponents worked so so hard to get rid of
If all of the damage is prevented, Mjlnir's effect no longer applies
If the gift was promised, that creature also gains indestructible until end of turn.
This card gives you a nice incentive to play out your hand, not to mention that it adds an extra card to any wheel effect that discards your hand to draw a new one
you'll look at six, finish resolving the ability, and then repeat the process twice more as the other instances of the ability resolve