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
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
If you do, that creature gains first strike until end of turn and must be blocked thus turn if able
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