Null Rod ($114) Null Rod is a mean stax card that shuts down some of the most relied upon cards in Commander, mana rocks
Ill go over a few examples of why some specific cards have been banned: Treasure Cruise + Dig Through Time [mtg_card]Treasure Cruise[/mtg_card] and [mtg_card]Dig Through Time[/mtg_card] are examples of cards that were individually too powerful for Modern (amongst other formats)
On the other hand, Grenzo prefers a wide board of creatures to steal spells, or even goad throngs of creatures for your own benefit
I personally have this card in a Grolnok, the Omnivore deck, and it can be a very powerful tool for getting additional cards at a low cost
There were also a few mechanical things that we had chosen to do as throughlines in Marvel sets
Thoughtseize is particularly good when you have either something to protect or something you need to prevent, and it just so happens that green can do both of those