Commander creatures you own have "Whenever this creature becomes tapped, it and other creatures you control that share a creature type with it each get +2/+0 and gain undying until end of turn." (When a creature with undying 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.)

{T}: Exile target creature card from a graveyard that was put there this turn. Create a token that's a copy of it, except it's a Nightmare in addition to its other types. Then exile all other Nightmare tokens you control.

Flying If an opponent would lose life during your turn, they lose twice that much life instead. (Damage causes loss of life.)

Flying, trample Pay 2 life: Surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Flying When this creature enters, if it was cast, each player exiles all but the bottom six cards of their library face down. At the beginning of your upkeep, draw a card.

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.) Whenever another nontoken creature dies, you may draw a card.

Flying Whenever another nontoken creature you control dies, you may exile it. If you do, create a token that's a copy of that creature, except it's 1/1 and it's a Nightmare in addition to its other types.

Flying, trample Pay 2 life, Sacrifice another creature: Search your library for a card, put that card into your hand, then shuffle.

Flying, lifelink Ward—Sacrifice three nonland permanents. If a card you didn't control would be put into an opponent's graveyard from anywhere, exile it instead. During your turn, you may play cards exiled with Valgavoth. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost.

Whenever you gain life, target opponent loses that much life. When Enduring Tenacity dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

As an additional cost to cast this spell, you may sacrifice any number of nonland permanents. This spell costs {1} less to cast for each permanent sacrificed this way. Whenever this creature enters or attacks, put a blight counter on it. Then for each blight counter on it, each opponent loses 4 life unless that player sacrifices a nonland permanent of their choice or discards a card.