Phyrexia vs. the Coalition
666 cards of Phyrexian hell and the Multiverse coalition opposing it! An artifacts, counters, and multicolor cube with one rare per pack, one retro artifact, and 13 nonrares.
NOTE: All Companions are errata'd to have the old companion rules, since that's better for limited.
Archetypes bridge across colors, but here are some guideposts:
: Affinity, Historic
: Artifacts, Instants & Sorceries in Graveyards
: Artifact and creature sacrifice, unearth
: Domain
: +1/+1 counters
: Legends, reanimator
: Prowess, artifacts
: Saprolings, sacrifice
: Modular, Equipment, Battle Cry
: Proliferate, ramp
: Golems
: Myr
Off-color kicker (and more) make splashing desirable, so many decks will dip into a third color (and with Sunburst & Converge, some will attempt all five!)