Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

Euroakus

When Euroakus enters, create a number of 1/1 blue Human Wizard creature tokens equal to the number of differently named lands you control.
{4}{G}{U}: Draw a card for each Wizard you control. They each get +1/+1 until end of turn for each card in your hand.

Kharis & The Beholder

Flying
When Kharis & The Beholder enters and at the beginning of your upkeep, create a 1/1 white Human creature token and make a charisma check. (Roll a d20.)
• If the result plus the number of creatures you control is greater than 11, put a +1/+1 counter on each creature you control.
• If the result is a natural 20, for each nonlegendary creature you control, create a token that's a copy of that creature.

Svega, the Unconventional

Landfall — Whenever a land enters under your control, put a loyalty counter on target planeswalker.
−2: For each planeswalker type among planeswalkers you control, create a 1/1 Attendee creature token that's all colors.
−X: Choose an Elspeth, Teferi, Liliana, Chandra, or Garruk planeswalker card name with mana value X. Create a copy of the card with the chosen name. You may cast the copy without paying its mana cost.
Svega can be your commander.

Myntasha, Honored One

As an additional cost to cast this spell, you may open a sealed Magic booster pack and put the cards on the bottom of your booster pile in a random order.
Spells you cast have booster cascade. (It's like cascade, but use your booster pile rather than your library.)

The Secret Lair

{T}: Add {C}.
{T}, Say the secret word: Add one mana of any color. Scry 1. You gain 1 life.

Wizard from Beyond

Create a Character (Any nonlegendary creature can choose this as its Background. It becomes legendary and can be your commander.)
Commander creatures you own are Clerics, Rogues, Warriors, and Wizards in addition to their other types.
As long as you have a full party, if an ability of a creature you control triggers, that ability triggers an additional time.

Diabolical Salvation

Split second
Create four 4/4 red Devil creature tokens with haste and "When this creature dies, create a colorless Treasure artifact token with '{T}, Sacrifice this artifact: Add one mana of any color.'" Sacrifice the Devil tokens at the beginning of the next end step.

The Legend of Arena

The Legend of Arena can be your commander.
I, II — Create a 2/1 red Human Wizard creature token. Spells you cast this turn cost {1} less to cast for each Wizard you control.
III — Search your library for a planeswalker card, put it onto the battlefield, then shuffle your library. It enters with an additional loyalty counter on it for each Wizard you control.

Fabled Path of Searo Point

{W}{U}{B}{R}{G}, {T}: Creatures you control gain landwalk until end of turn.

Inzerva, Master of Insights

+2: Draw two cards, then discard a card.
−2: Look at the top two cards of each other player's library, then put any number of them on the bottom of that library and the rest on top in any order. Scry 2.
−4: You get an emblem with "Your opponents play with their hands revealed" and "Whenever an opponent draws a card, this emblem deals 1 damage to them."