msem-instigator

First mate—Your starting deck contains twelve or more creature cards and they all share a creature type.
As Adam of the Ironside enters the battlefield, choose a creature type. Adam becomes that type.
Adam gets +1/+1 for each other creature you control of the chosen type.

First mate—At least half the cards in your starting deck are lands. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Trample
{1}, Discard a land card: Put a +1/+1 counter on Alvarez. He deals 1 damage to any target.

First mate—Your starting deck contains no creature cards. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Prowess
Whenever Garth attacks, look at the top card of your library. If it's an instant or sorcery card, you may cast it. (You still pay its costs.)

First mate—Your starting deck contains at least twelve Vehicles. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Haste
{R}{W}, {T}: You may put a Vehicle card from your hand onto the battlefield. That Vehicle gains haste and becomes an artifact creature until end of turn.

First mate—Each nonland card in your starting deck has the same name as exactly one other card in your starting deck.
Vigilance
Whenever you cast a spell with the same name as a card in your graveyard, draw a card.

First mate—Your starting deck contains only cards with mana value 0, 1, or 3. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Menace
Once each turn, when one or more sources you control deal damage, you may put a +1/+1 counter on Hugo.

First mate—Each nonland card in your starting deck is an instant or has flash. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Flash
When Mable enters the battlefield, you gain 2 life and draw a card.

First mate—Each nonland card in your starting deck has “destroy,” “die,” “graveyard,” and/or “mill” in its printed rules text. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Deathtouch
When Marisa enters the battlefield, if it was cast, you may put target permanent card from a graveyard onto the battlefield under your control.

First mate—Each nonland card in your starting deck targets or has an ability that targets. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Hexproof
Whenever a permanent you don't control becomes the target of a spell or ability you control, create a token that's a copy of that permanent.

First mate—Your starting deck contains no more than eight cards of each nonland card type. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Lifelink
At the beginning of your upkeep, you may pay 3 life. If you do, exile another target nonland permanent until Tabia leaves the battlefield. If you control another permanent that shares a card type with it, exile it instead.

First mate—There are four or fewer different mana costs among nonland cards in your starting deck. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
First strike
Each spell your opponents cast that would cost less than three mana to cast costs {1} more to cast.