Interaction Question: I have a Hallowed Spiritkeeper in play and a bunch of tokens (I have no creatures in the graveyard). My opponent boardwipes. How I think that would work is that Spiritkeeper and the tokens go to the graveyard, the Spiritkeeper effect triggers, checking and seeing a bunch of tokens in the graveyard and creating a bunch of tokens, then the tokens in the graveyard stop existing 'cause of state-based actions. I don't know if this is right though. I'd like if you could explain.
You’re not right for a couple of reasons.
Let’s start with what actually happens: When all your creatures die, Hallowed Spiritkeeper’s ability triggers but doesn’t go on the stack yet. After the board wipe finishes resolving, state-based actions are checked and the tokens in your graveyard cease to exist. After state-based actions are done, triggers are put on the stack. When Hallowed Spiritkeeper’s trigger resolves, it counts the number of creature cards in your graveyard at that time and makes that many tokens.
So, state-based actions are checked long before the trigger resolves, and even if somehow Spiritkeeper cared about the number at the time it died, it wouldn’t count the tokens because tokens aren’t cards and it cares about creature cards.