I think that the discard and deal three options are the most powerful of the six, while the remaining of the four are the flex choices depending on the situation
Not after you begin casting the Emerge spell
Desecration Demon always seems nice enough when building as you don't have to think about it too much, just a nice good value 6/6 flier for the bargain cost of 4
If you exile a creature card to Werewhat's enters ability, Werewhat will be a transforming double-faced card for as long as it remains on the battlefield
Complicating this plan is that these cards, as reskins of some legendary comic book covers, will pull interest from those same comic collectors
Like Mothra before it, what Valkyries Call truly does is grant your creatures a variant of undying that Wizards hopes in vain isnt so trivial to circumvent and go infinite