Whenever you cast a noncreature spell, counter that spell. Create a number of 1/1 blue Merfolk creature tokens equal to the amount of mana spent to cast that spell.

Whenever Olinda enters or attacks, for each opponent, put an odor counter on up to one target creature that player controls without an odor counter on it. Each of those creatures has "At the beginning of your upkeep, you lose 2 life" for as long as it has an odor counter on it. (They continue to smell after Olinda has left the battlefield.)

Rulebreaker — If Tolabow, Loch Rascal is your commander, the color identity of instant and sorcery cards in your deck can include one color of your choice not in your commander's color identity, and your deck can have any basic land cards.
Whenever you cast an instant or sorcery spell, create a 1/1 blue and red Otter creature token with prowess. (Whenever you cast a noncreature spell, it gets +1/+1 until end of turn.)

Whenever The Madcap Jester attacks, each opponent exiles the top card of their library.
Whenever a spell or ability you control causes one or more cards to be exiled from an opponent's library, you may play those cards until the end of your next turn. Mana of any type can be spent to cast spells this way.

Flying, trample, protection from Angels and from Archons
Players can't gain life.
When Balefang enters, target opponent creates a tapped Baneslayer Angel token. The token is goaded for the rest of the game. (It's a 5/5 Angel creature with flying, first strike, lifelink, and protection from Demons and from Dragons.)

+1: Create two tapped Powerstone tokens. (They're artifacts with ": Add . This mana can't be spent to cast a nonartifact spell.")
−X: Untap X target artifacts.
−6: Search your library for an artifact card, put it onto the battlefield, then shuffle.
Dyfed, the Guiding Hand can be your commander.

Rulebreaker — A deck with this commander can have Angel cards of any color identity and any basic land cards.
Flying
Whenever Seluma deals combat damage to a player, return target Angel creature card from your graveyard to the battlefield.

Each nontoken creature you control that wasn't cast from your hand enters with two additional +1/+1 counters on it.
+1: Exile up to one other target permanent you control. At the beginning of the next end step, return that card to the battlefield under its owner's control.
−2: For each opponent, return up to one target nonland permanent that player controls to its owner's hand.
Venser, Visionary Traveler can be your commander.

Whenever an artifact is put into a graveyard from the battlefield, put a number of +1/+1 counters equal to that artifact's mana value on Joven and Chandler.
, : Gain control of target artifact until end of turn. Untap it. It gains haste until end of turn.

+2: Create a 2/2 black Zombie creature token.
0: You may sacrifice a creature. If you do, add .
−5: Create a Lord of the Pit token. (It's a 7/7 Demon creature with flying, trample, and "At the beginning of your upkeep, sacrifice another creature. If you can't, this token deals 7 damage to you.")
Thomil, the Destroyer can be your commander.

Hexproof
When Autumn Willow enters, create a 1/1 green Forest Dryad land creature token. (It's affected by summoning sickness.)
Whenever you tap a land creature for mana, add an additional .

+2: Arzakon deals 3 damage to any other target.
−3: Create a Black Lotus token. (It's a artifact with ", Sacrifice this token: Add three mana of any one color.")
−7: Each player shuffles their hand and graveyard into their library, then draws seven cards.
Arzakon can be your commander.

Menace
At the beginning of your end step, target opponent may draw four cards. If they do, look at that player's hand and you may cast a spell from their hand without paying its mana cost. If they don't, put two +1/+1 counters on Kuroki.

Trample, hexproof, indestructible

Protection from red
Whenever you cast your first spell during each opponent's turn, draw three cards, then put two cards from your hand on top of your library in any order.

Trample, indestructible
When Tresserhorn's Lord enters, sacrifice him unless you sacrifice three creatures, pay 3 life, and have target opponent draw three cards.
Whenever you sacrifice a creature, draw a card.

Whenever a creature dies, target opponent loses 1 life and you gain 1 life.
+1: Goad up to two target creatures.
−6: Each opponent exiles the top two cards of their library. Until end of turn, you may play those cards without paying their mana costs.
Sifa Grent can be your commander.

When Chief Magistrate of Mercadia enters, you become the monarch.
At the beginning of your upkeep, create a 2/1 red Goblin creature token with haste. Then if you're the monarch, for each creature token you control, create a token that's a copy of it.

Rulebreaker — A deck with this commander can have artifact creature and Equipment cards of any color identity and any basic land cards.
Whenever you cast an artifact creature or Equipment spell, you may copy that spell. Do this only once each turn. (The copy becomes a token.)

Flying, lifelink
If you would gain life, you gain twice that much life instead.
When Selenia dies, create a legendary black Aura Curse enchantment token named Selenia's Curse attached to target opponent. The token has enchant player and "If enchanted player would lose life, they lose twice that much life instead."

Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever The Weaver King deals combat damage to a player, they mill that many cards. Then for each opponent, put a creature card from that player's graveyard that was put there from their library this turn onto the battlefield under your control.

+2: Create a Giant Badger token. (It's a 2/2 Badger creature with "Whenever this token blocks, it gets +2/+2 until end of turn.")
−3: Mill three cards. Put all permanent cards from among them into your hand.
−8: Until end of turn, creatures you control have base power and toughness 8/8 and gain trample.
Greensleeves can be your commander.

+2: Create two 1/1 blue Bird creature tokens with flying.
0: Draw a card. You may put a permanent card with mana value 4 or less from your hand onto the battlefield.
−7: Create a Feroz's Ban token. (It's a artifact with "Creature spells cost more to cast.")
Feroz, Ulgrotha's Warden can be your commander.

Flying
Once during each of your turns, you may pay rather than pay the mana cost for a spell you cast from exile.
Whenever Dragon's Smile deals combat damage to a player, that player exiles that many cards from the top of their library. You may play those cards this turn.
Crew 3

Rulebreaker — A deck with this commander can have any land cards.
Whenever Grizzlegom attacks, create a 1/1 white Soldier creature token for each Plains you control. Draw a card for each Island you control. Each opponent loses 1 life for each Swamp you control. Put a +1/+1 counter on Grizzlegom for each Mountain you control. You gain 1 life for each Forest you control.

Whenever you cast a permanent spell with in its mana cost or activate an ability with in its activation cost that isn't a mana ability, you may have the value of X become 5. Do this only once each turn.

Rulebreaker — A deck with this commander can have creature cards with mana value 7 or greater of any color identity and any basic land cards.
Whenever a creature you control with mana value 7 or greater attacks, double its power and toughness until end of turn.