Seasoned Dungeoneer

When Seasoned Dungeoneer enters, you take the initiative.
Whenever you attack, target attacking Cleric, Rogue, Warrior, or Wizard gains protection from creatures until end of turn. It 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 the creature, then put the card back or put it into your graveyard.)

Gandalf, White Rider

Vigilance
Whenever you cast a spell, creatures you control get +1/+0 until end of turn. Scry 1.
When Gandalf, White Rider dies, you may put it into its owner's library fifth from the top.

Deep Gnome Terramancer

Flash
Mold Earth — Whenever one or more lands enter under an opponent's control without being played, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle. Do this only once each turn.

Tenacious Underdog

Blitz—{2}{B}{B}, Pay 2 life. (If you cast this spell for its blitz cost, it gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step.)
You may cast Tenacious Underdog from your graveyard using its blitz ability.

Lae'zel, Vlaakith's Champion

If you would put one or more counters on a creature or planeswalker you control or on yourself, put that many plus one of each of those kinds of counters on that permanent or player instead.
Choose a Background (You can have a Background as a second commander.)

Nalia de'Arnise

You may look at the top card of your library any time.
You may cast Cleric, Rogue, Warrior, and Wizard spells from the top of your library.
At the beginning of combat on your turn, if you have a full party, put a +1/+1 counter on each creature you control and those creatures gain deathtouch until end of turn.

Preacher of the Schism

Deathtouch
Whenever Preacher of the Schism attacks the player with the most life or tied for most life, create a 1/1 white Vampire creature token with lifelink.
Whenever Preacher of the Schism attacks while you have the most life or are tied for most life, you draw a card and you lose 1 life.

Grim Hireling

Whenever one or more creatures you control deal combat damage to a player, create two Treasure tokens.
{B}, Sacrifice X Treasures: Target creature gets -X/-X until end of turn. Activate only as a sorcery.

Lotho, Corrupt Shirriff

Whenever a player casts their second spell each turn, you lose 1 life and create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Squad Commander

When Squad Commander enters, create a 1/1 white Kor Warrior creature token for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)
At the beginning of combat on your turn, if you have a full party, creatures you control get +1/+0 and gain indestructible until end of turn.

Harper Recruiter

Flying
Whenever Harper Recruiter attacks, look at the top four cards of your library. You may reveal a Cleric card, a Rogue card, a Warrior card, and/or a Wizard card from among them and put those cards into your hand. Put the rest on the bottom of your library in a random order.

Redemption Choir

Lifelink
Coven — Whenever Redemption Choir enters or attacks, if you control three or more creatures with different powers, return target permanent card with mana value 3 or less from your graveyard to the battlefield.