While theres a lot of synergy here, the cards are mostly strong independently, and the deck is designed to play a fair, interactive game that just happens to be able to gain infinite life with Urza and the Thopter Foundry / Sword of the Meek Combo, but mostly Urza, Oko, and Emry are all amazing standalone cards that require fairly different answers
However, as this theme develops and new proposals emerge, more specific answers will need to be released to establish a limiter that keeps the Metagame in a healthy state
The automatic actions that take place during the cleanup step are: First, the active player (if it's your turn, that's you) discards enough cards to comply with the maximum hand size
Legendary Creature - Eldrazi Kozilek's Unsealing Devoid (This card has no color.) Whenever you cast a creature spell with mana value 4, 5, or 6, create two 0/1 colorless Eldrazi Spawn creature tokens with "Sacrifice this token: Add ." Whenever you cast a creature spell with mana value 7 or greater, draw three cards
By running zero basic lands in your deck, a trivial task in todays Commander meta, one activation of this Druid flips your entire library into your graveyard
The Phyrexian deck is very strong and fairly valuable