Trample
Whenever Yidris deals combat damage to a player, as you cast spells from your hand this turn, they gain cascade. (When you cast the spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Tokens you control have ": Add ."
Choose a Background (You can have a Background as a second commander.)

(: Add or .)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

+1: Up to one target creature gets -2/-1 until your next turn.
−2: Mill two cards, then you may return a creature card from your graveyard to your hand.
−7: You get an emblem with "At the beginning of your end step, create X 2/2 black Zombie creature tokens, where X is two plus the number of Zombies you control."

Choose target creature you control. Each other creature becomes a copy of that creature until end of turn, except it isn't legendary.

Whenever you cast an instant or sorcery spell, flip a coin. If you lose the flip, return that spell to its owner's hand. If you win the flip, copy that spell, and you may choose new targets for the copy.
Partner (You can have two commanders if both have partner.)

Flying
, Pay 2 life: Target creature gets -1/-1 until end of turn.
Whenever you lose life, draw that many cards. (Damage causes loss of life.)

Echo (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When this creature enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

When you cast this spell, if you have fewer than seven cards in hand, draw cards equal to the difference.
Menace
Discard a card with mana value X: Counter target spell with mana value X.

Each player shuffles their hand and graveyard into their library, then draws seven cards. Exile Time Reversal.

( represents colorless mana.)
When this creature enters, target opponent reveals their hand. You choose a nonland card from it and exile that card.
When this creature leaves the battlefield, target opponent draws a card.

Reach
Whenever Six attacks, mill three cards. You may put a land card from among them into your hand.
During your turn, nonland permanent cards in your graveyard have retrace. (You may cast permanent cards from your graveyard by discarding a land card in addition to paying their other costs.)

: Add one mana of any color.
Whenever you tap this land for mana, target opponent creates a 1/1 colorless Spirit creature token.

As an additional cost to cast this spell, sacrifice a creature.
Add .

Flying
Whenever you draw a card, Niv-Mizzet deals 1 damage to any target.
: Draw a card.

, : Target creature you control fights another target creature.

+2: You gain 3 life.
0: You draw a card and lose 1 life.
−3: Destroy target creature.
−6: You get an emblem with "Whenever you gain life, target opponent loses that much life."

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 this creature dies, if it had no time counters on it, you may search your library for an enchantment card, put it onto the battlefield, then shuffle.

Players can't untap more than one creature during their untap steps.

(: Add or .)
As this land enters, you may pay 2 life. If you don't, it enters tapped.