{T}, Pay 1 life, Sacrifice an artifact or creature: Make a pledge.

Revered
{T}: Add {G}.

Enchant creature with another Aura attached to it
Enchanted creature gets +3/+3 and has trample, vigilance, and reach.

When Everpresent Rot enters, create a 1/1 green Saproling creature token, surveil 1, then you gain 1 life.
When one or more permanent cards leave your graveyard, return Everpresent Rot to its owner's hand.

Deathtouch
Other Gorgons, Snakes, and Basilisks you control get +1/+1.
Whenever a creature with deathtouch you control deals combat damage to a player or planeswalker, create a Treasure token.

When this creature enters, target player separates their hand into a face-up pile and a face-down pile. Choose one of those piles, reveal it, and choose a nonland card from it. Exile that card until this creature leaves the battlefield.

Trample, haste
Decayed

Exile the top two cards of your library. You may play those cards until you next cast a spell from your hand.
Flashback {3}{R}{R}

Cards in graveyards can't leave the graveyard.
Cycling {2}

As an additional cost to cast this spell, sacrifice a creature.
Fall Upon Your Blade deals damage equal to the sacrificed creature's power to any target.
Cycling {2}

Whenever a creature you control attacks alone, you may pay {1}{B}. If you do, return this card from your graveyard to the battlefield tapped and attacking.

Creatures can't attack you or a planeswalker you control unless their controller pays {1} for each of those creatures beyond the first.

Target player mills two cards, then mills two more cards for each card named Fathomless Dominion in your graveyard.

Defender
When Feasting Sloth enters, create a Berry token.
Feasting Sloth can attack as though it didn't have defender if it's enchanted, equipped, or has a counter on it.

Once each turn, when you activate a nonmana ability, you may put a +1/+1 counter on Feeble Fish. Then if there are three or more +1/+1 counters on it, remove them all and transform it.

Destroy target creature if its mana value is less than or equal to the amount of mana spent to cast this spell.
Flashback {X}{B}{B}{B}

When Flags on High enters, create two 1/1 colorless Soldier creature tokens.
{1}{R}, Sacrifice Flags on High: Target creature you control gets +1/+0 and gains haste until end of turn. Activate only as a sorcery.

Flame Whip deals 4 damage to target creature or planeswalker.

Haste
Whenever a player casts a spell, if no mana from a basic source was spent to cast it, Flaw in the System deals 2 damage to that player.

Enchant creature you control
Enchanted creature gets +1/+1.
When this Aura enters, enchanted creature fights up to one target creature.

Return target creature to its owner's hand. If you've cast another instant or sorcery spell this turn, draw a card.

Destroy target creature or enchantment. You lose life equal to its mana value.

Equipped creature gets +2/+2 and can't be blocked by more than one creature.
Equip {4}

Choose target card in another player's graveyard other than a basic land. Search its owner's graveyard, hand, and library for any number of cards with the same name as that card and exile them. If their library is searched this way, they shuffle it. You gain 1 life for each card exiled this way. That player draws a card for each card exiled from their hand this way.
Flashback {3}{B}

{T}: Add {C}. You may sacrifice Fortune Bearer. If you don't, you can't spend this mana to cast a spell from your hand.
Surface {5}{U}{U}. Fortune Bearer surfaces transformed.