Cloud, Midgar Mercenary Stoneforge Mystic used to be on the banned list
With both in play, youd create a mutagen token every time a creature leaves the battlefield, along with a food token and +1/+1 counter on a single creature every time you attack
Any cheaper than that and this starts to become absolutely ridiculous
Each spell with tiered has a base cost as well as multiple modes, each with their own additional costs
Similarly, you can't pay a cost that includes the payment of any amount of life other than 0 life
It would be easy to add many more cards to this tier, but I have deliberately aimed to be selective here in order to show off the cards I actually think are strong, rather than cards that will see play as a 1-of or in some fringe deck