Though Nefeltari Vivi also known as the slightly different Nefertari Vivi, depending on the translation from the Japanese text debuted long before the arcs featured in Kingdoms of Intrigue, she joined the Straw Hat Pirates during the Arabasta arc
They dump a bunch of strong creatures into their graveyard and then plan to reanimate them
Isochron Scepter and Arcane Bombardment do this because they dont have an object on the stack to copy
Like all the modal DFCs, just having the option for a tapped land, or an untapped land for cost, is quite powerful.
A powerful pump spell on the adventure side, plus a good creature to follow up, doing a 1-2 punch with this in the mid-game gets a lot of damage through
Rottenmouth Viper, on the other hand, is exceedingly strong in any black deck even when cast at 6 mana, but squirrels ability to dump out Food tokens onto the battlefield early makes it castable at 4 or 5 mana most games, making it an early must-answer threat that will dominate the game