mtg cumulative upkeep cards Halls of Mist [Ice Age] then sacrifice it unless you pay its upkeep cost for each age counter on it.) Wall of Shards | Coldsnap

One card is never going to make or break your deck

And, on the gamification side of the app, there is also a rewards system with which users can gain points (called "dragon dust") that can soon be redeemed for goodies

For one and a hybrid Simic mana, both Tatsunari and target Frog I control can't be blocked this turn except by creatures with flying or reach

Mazirek, Kraul Death Priest is a five-mana 2/2 flyer that grants every creature you control a +1/+1 counter whenever a creature gets sacrificed

and a pile of card advantage options make this an easy inclusion at the top-end

that's for your opponents to worry about instead