Fandaniel, Telophoroi Ascian

Whenever you cast an instant or sorcery spell, surveil 1.
At the beginning of your end step, each opponent may sacrifice a nontoken creature of their choice. Each opponent who doesn't loses 2 life for each instant and sorcery card in your graveyard.

Cleon, Merry Champion

Double strike
Heroic — Whenever you cast a spell that targets Cleon, exile the top card of your library. You may play that card until the end of your next turn.

Kinzu of the Bleak Coven

Flying
Whenever another nontoken creature you control dies, you may pay 2 life and exile it. If you do, create a token that's a copy of that creature, except it's 1/1 and has toxic 1. (Players dealt combat damage by it also get a poison counter.)

Sivriss, Nightmare Speaker

{T}, Sacrifice another creature or an artifact: For each opponent, you mill a card, then return that card from your graveyard to your hand unless that player pays 3 life. (To mill a card, put the top card of your library into your graveyard.)
Choose a Background (You can have a Background as a second commander.)

Horobi, Death's Wail

Flying
Whenever a creature becomes the target of a spell or ability, destroy that creature.

Baldin, Century Herdmaster

During your turn, each creature assigns combat damage equal to its toughness rather than its power.
Whenever Baldin attacks, up to one hundred target creatures each get +0/+X until end of turn, where X is the number of cards in your hand.

Agent of the Iron Throne

Commander creatures you own have "Whenever an artifact or creature you control is put into a graveyard from the battlefield, each opponent loses 1 life."

Mastermind Plum

Whenever Mastermind Plum attacks, exile up to one target card from a graveyard. If an artifact card was exiled this way, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Whenever you cast a spell, if mana from a Treasure was spent to cast it, you draw a card and you lose 1 life.

Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis.

Seizan, Perverter of Truth

At the beginning of each player's upkeep, that player loses 2 life and draws two cards.

Ghoulcaller Gisa

{B}, {T}, Sacrifice another creature: Create X 2/2 black Zombie creature tokens, where X is the sacrificed creature's power.

Kain, Traitorous Dragoon

Jump — During your turn, Kain has flying.
Whenever Kain deals combat damage to a player, that player gains control of Kain. If they do, you draw that many cards, create that many tapped Treasure tokens, then lose that much life.

Sauron, the Necromancer

Menace
Whenever Sauron attacks, exile target creature card from your graveyard. Create a tapped and attacking token that's a copy of that card, except it's a 3/3 black Wraith with menace. At the beginning of the next end step, exile that token unless Sauron is your Ring-bearer.

Patron of the Nezumi

Rat offering (You may cast this spell any time you could cast an instant by sacrificing a Rat and paying the difference in mana costs between this and the sacrificed Rat. Mana cost includes color.)
Whenever a permanent is put into an opponent's graveyard, that player loses 1 life.