Getting a bunch of 0/1 creatures is a great way to shield your life total from many threats with haste after a Day of Judgment, and then you can sacrifice those that make it to your turn to rebuild your board position with minimal fuss, and possibly even a Blood Artist trigger or three
You may play those cards until your next end step
An extra upkeep is just another upkeep step that can be added to your turn, usually directly after your normal upkeep
Get ready for the new era of this Wurm's dominance to begin
Liliana, Dreadhorde General Could anyone else make my Top Ten list
Luckily with cards like Command Tower, City of Brass, Reflecting Pool, #1 below and more, getting that mana is easier than ever