The best ones to do that are artifacts, so any drafter can use them, but some colored ones look interesting as well: And to help with critical mass, there are some Changelings and clones that are commonly used anyway: Ideally, the effect I want to achieve is: - 1-2 decks per pod have minor tribal themes (say, RG Beatdown with Krenko, Mob Boss, Siege-Gang Commander and Goblin Warchief doing cute things) - In about 50% of the drafts, a dedicated tribal deck is drafted, running the generic tribe enablers (White weenie running mostly Soldiers with Adaptive Automaton, Harsh Mercy, Mutavaultand Obelisk of Urd) - Once in a blue moon, someone puts together Shriekmaw, Mulldrifter, Flickerwisp, some clones, changelings and the tribal cards and makes a crazy 4-color Elementals blink deck that's bad but loads of fun

For that, you needed Urza firing on all cylinders, but without the Ancient Stirrings and Sylvan Scryings of Mono-Green Tron, you couldnt rely on that happening in any given game and couldnt load up on these big mana payoffs and this in turn meant you werent rewarded well for assembling Tron
Energy requirements
Most modern super rare cards are are full art cards (and those are awesome), but these amazing rares truly highlighted legendary/mythical Pokmon in a new, colorful, unique way that stood out among any other card rarity