They keep undying until end of turn, so we could also do some spell casting that involves creature sacrifice, as well as activating abilities
Godzilla, King of Monsters) is complicated: Decreasing a creature's power below 0 doesn't necessarily destroy them, because the rule is about damage
Pack Rat Pack Rat not only gains power from the other rats you control, it also gains toughness
Other than a stint on the List, Keeper of the Nine Gales has never had a reprint since, so it makes perfect sense that it was susceptible to a spike
(2/1/2014) If Jeleva enters the battlefield without being cast, then no mana was spent to cast it
The short of it is that you can exile her at the beginning of your upkeep, and then whenever a land enters, you can either bring her back or put a voyage counter on her