Regenerate each creature you control.

Equipped creature gets +2/+2 and has protection from green and from blue.
Whenever equipped creature deals combat damage to a player, you create a 2/2 green Wolf creature token and that player mills ten cards.
Equip

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Trample
When this creature enters, destroy target noncreature permanent.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

All permanents are colorless.

Flying
White spells and black spells you cast cost less to cast.

Destroy all non-Rat creatures. They can't be regenerated, of course. Then each player amasses Rats X, where X is the number of Rats they control.

Rivendell enters tapped unless you control a legendary creature.
: Add .
, : Scry 2. Activate only if you control a legendary creature.

Creatures you control gain indestructible. Take an extra turn after this one. At the beginning of that turn's end step, you lose the game.

Each nonland card in your graveyard has escape. The escape cost is equal to the card's mana cost plus exile three other cards from your graveyard. (You may cast cards from your graveyard for their escape cost.)
At the beginning of the end step, sacrifice this enchantment.

Ward—Discard an enchantment, instant, or sorcery card.
Whenever you cast your second spell each turn, each opponent mills two cards. When one or more cards are milled this way, exile target enchantment, instant, or sorcery card with equal or lesser mana value than that spell from an opponent's graveyard. Copy the exiled card. You may cast the copy without paying its mana cost.

Knight creatures you control have double strike.

Whenever another permanent you control becomes the target of a spell or ability an opponent controls, you may return that permanent to its owner's hand.

Start your engines!
: Add .
Max Speed — , : Mill seven cards. Choose a playtest card from among them. You may cast it without paying its mana cost. If Team Cloudspire won the race, copy it and you may choose new targets for the copy. If Team Speed Demons won the race, each opponent loses life equal to its mana value.
The Mystery Raceway can be your commander.

: Creatures you control get +1/+0 and gain haste until end of turn.
When this creature enters, discard any number of cards, then draw that many cards.
When this creature dies, it deals X damage to each opponent and each planeswalker they control, where X is the number of land cards in your graveyard.

Enchant creature
As long as enchanted creature is green, it gets +1/+1 and has indestructible. (Damage and effects that say "destroy" don't destroy it. If its toughness is 0 or less, it still dies.)
As long as enchanted creature is white, it gets +1/+1 and has flying.

Destroy all creatures. They can't be regenerated.

Flying, trample
When this creature enters, search your library for a card, put it into your hand, shuffle, then discard a card at random.

Flying, trample
Shroud (This creature can't be the target of spells or abilities.)

: Add .
: Add or . This land deals 1 damage to you.