You can save a ton of mana on the best activated abilities with this cost reducer, and there are others, but none are as efficient and come online as fast as Training Grounds
Obviously, if people start playing a ton of anti-creature cards that match up well against Izzet, we could also go the other way, starting as a Thousand-Year deck and transforming into creatures later
Pyrohemia + Pestilence Pestilence and its Planar Chaos twin Pyrohemia can split up damage across different turns and deal damage in increments of 1, which matters for damage amplifiers and effects like Ob Nixilis, Captive Kingpin and Ghyrson Starn, Kelermorph
However, it will also give you 8 additional booster packs, where you can find other rare cards
On the left, theres a dense cluster of tiny sets: Secret Lairs (limited-run promotional sets, typically 510 cards), Commander preconstructed decks, and various special releases