Pandemonium

Whenever a creature enters the battlefield, that creature's controller may have it deal damage equal to its power to any target of their choice.

Mage Slayer

Whenever equipped creature attacks, it deals damage equal to its power to the player or planeswalker it's attacking.
Equip {3}

The Triumph of Anax

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
I, II, III — Until end of turn, target creature gains trample and gets +X/+0, where X is the number of lore counters on The Triumph of Anax.
IV — Target creature you control fights up to one target creature you don't control. (Each deals damage equal to its power to the other.)

Alpha Authority

Enchant creature
Enchanted creature has hexproof and can't be blocked by more than one creature.

Warstorm Surge

Whenever a creature enters the battlefield under your control, it deals damage equal to its power to any target.

Artifact Mutation

Destroy target artifact. It can't be regenerated. Create X 1/1 green Saproling creature tokens, where X is that artifact's mana value.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Electropotence

Whenever a creature enters the battlefield under your control, you may pay {2}{R}. If you do, that creature deals damage equal to its power to any target.

Aspect of Mongoose

Enchant creature
Enchanted creature has shroud. (It can't be the target of spells or abilities.)
When Aspect of Mongoose is put into a graveyard from the battlefield, return Aspect of Mongoose to its owner's hand.

Thromok the Insatiable

Devour X, where X is the number of creatures devoured this way (As this enters the battlefield, you may sacrifice any number of creatures. This creature enters the battlefield with X +1/+1 counters on it for each of those creatures.)

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}