mtg edge of eternities booster box price Magic: The Gathering a star system teeters on the brink of disaster If you have ~$400 for

The Everflowing Well / The Myriad Pools The Everflowing Well offers a lot of potential card advantage

It also means they can't efficiently dump stuff like Path to Exile on your Emrakul before you get use it yourself on their stuff

Cards that genuinely take advantage of this are few and far between, so your best use of Serras Sanctum would simply be to put it in an enchantress deck.

Note that's not planeswalkers so you cannot target them for loyalty counter doubling since it says each kind of counter, not just +1/+1, like Shield or energy counters on artifacts (or...say....fellowship counters...) She's great fun for the masses leading a Commander deck