Chronozoa

Flying
Vanishing 3 (This creature enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Chronozoa dies, if it had no time counters on it, create two tokens that are copies of it.

Astrid Peth

Whenever Astrid Peth enters or attacks, create a Food token.
Brand-new Sky — Whenever you sacrifice a Clue or Food, Astrid Peth explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Idris, Soul of the TARDIS

Vanishing 3
Imprint — When Idris, Soul of the TARDIS enters, exile another artifact you control until Idris leaves the battlefield.
Idris has all activated and triggered abilities of the exiled card and gets +X/+X, where X is the exiled card's mana value.

Lavacore Elemental

Vanishing 1 (This creature enters with a time counter on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Whenever a creature you control deals combat damage to a player, put a time counter on Lavacore Elemental.

Jhoira's Timebug

{T}: Choose target permanent you control or suspended card you own. If that permanent or card has a time counter on it, you may remove a time counter from it or put another time counter on it.

The Tenth Doctor

Allons-y! — Whenever you attack, exile cards from the top of your library until you exile a nonland card. Put three time counters on it. If it doesn't have suspend, it gains suspend.
Timey-Wimey — {7}: Time travel three times. Activate only as a sorcery. (For each suspended card you own and each permanent you control with a time counter on it, you may add or remove a time counter. Then do it two more times.)

Rose Tyler

Rose Tyler gets +1/+1 for each time counter on it.
Bad Wolf — Whenever Rose Tyler attacks, put a time counter on it for each suspended card you own and each other permanent you control with a time counter on it.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Aeon Chronicler

Aeon Chronicler's power and toughness are each equal to the number of cards in your hand.
Suspend X—{X}{3}{U}. X can't be 0.
Whenever a time counter is removed from Aeon Chronicler while it's exiled, draw a card.

Atraxi Warden

Flying
When Atraxi Warden enters, exile up to one target tapped creature.
Suspend 5—{1}{W} (Rather than cast this card from your hand, you may pay {1}{W} and exile it with five time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Flesh Duplicate

You may have Flesh Duplicate enter as a copy of any creature on the battlefield, except it has vanishing 3 if that creature doesn't have vanishing. (A permanent with vanishing 3 enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)

Kate Stewart

Whenever you put one or more time counters on a permanent you control, create a 1/1 white Soldier creature token.
Whenever Kate Stewart attacks, you may pay {8}. If you do, attacking creatures get +X/+X until end of turn, where X is the number of time counters among permanents you control.

Dinosaurs on a Spaceship

Vigilance, trample
Other Dinosaurs you control get +1/+1 and have vigilance and trample.
Suspend 4—{3}{R}{W}
Whenever a time counter is removed from Dinosaurs on a Spaceship while it's exiled, create a 2/2 red and white Dinosaur creature token with flying and haste.

Amy Pond

Partner with Rory Williams (When this creature enters, target player may put Rory into their hand from their library, then shuffle.)
Whenever Amy Pond deals combat damage to a player, choose a suspended card you own and remove that many time counters from it.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Judoon Enforcers

Trample
No more than one creature can attack you each combat.
Suspend 6—{1}{R}{W} (Rather than cast this card from your hand, you may pay {1}{R}{W} and exile it with six time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Gandalf of the Secret Fire

Whenever you cast an instant or sorcery spell from your hand during an opponent's turn, exile that card with three time counters on it instead of putting it into your graveyard as it resolves. Then if the exiled card doesn't have suspend, it gains suspend. (At the beginning of your upkeep, remove a time counter. When the last is removed, you may play it without paying its mana cost.)