Mayhem is the featured mechanic of the black-red color pair that Green Goblin lives in for this set, and is a bit of a twist on an existing mechanic called Madness
Commander has a ton of powerful ways to generate a bunch of mana, and turning that mana into cards, life, and a Jellyfish Hydra Beast that flies and tramples is pretty much everything you want to be doing in the format
The 4/2 Plant tokens address a common problem with ramp cards, that they make you pass the turns where you cast them, giving Regrowth a leg-up on the competition
From September 26th to November 11th, Two-Headed Giant Commander Nights will also have this as a promo
These can fetch a nice premium if sold to the right collectors
Geometric Nexus Geometric Nexus scales well since it counts spells cast by all players, but the costs are still too high