The second card was Up the Beanstalk, a throwaway uncommon from Wilds of Eldraine that was intended to support a limited archetype about casting expensive stuff but ended up being hilariously broken in just about every format it was legal in
Jor Kadeen can be buffed with equipment and auras to make it a significant threat thanks to trample, especially with commander damage
Since rats are predominantly black cards, strategies often involve generating a lot of weaker creatures and/or creature tokens so you can make a lot of sacrifices to fill up your graveyard
Meanwhile, Up The Beanstalk was deemed too efficient a card-draw option, and it doesn't help that players don't have to pay 5 mana when they're using the Evoke elementals (at least Fury is gone now)
Agent of the Shadow Thieves plays quite well alongside blacks many ways to pay life for beneficial effect, making your commander(s) quite potent attackers against whoever is unfortunate enough to have the most life
FluctuatorFluctuator is different, though, because Cycling itself is different