Spells you cast but don't own cost less to cast.
Whenever one or more creatures you control deal combat damage to a player, look at the top card of that player's library, then exile it face down. You may play that card for as long as it remains exiled, and mana of any type can be spent to cast that spell.

, Sacrifice this creature: Draw a card.
Dredge 1

Whenever Haliya enters or attacks, put a +1/+1 counter on target creature you control.
Whenever one or more creatures you control with +1/+1 counters on them deal combat damage to a player, draw a card.

When Hama enters, target opponent mills three cards. Exile up to one noncreature, nonland card from that player's graveyard. For as long as you control Hama, you may cast the exiled card during your turn by waterbending rather than paying its mana cost, where X is its mana value.

Whenever a creature you control is turned face up, it endures X, where X is that creature's toughness.
Landfall — Whenever a land you control enters, seek a creature card and manifest it.

When Hapatra enters, for each opponent, put X -1/-1 counters on up to one target creature that player controls, where X is the greatest mana value among cards in your graveyard.

Flying
When Hidetsugu and Kairi enters, draw three cards, then put two cards from your hand on top of your library in any order.
When Hidetsugu and Kairi dies, exile the top card of your library. Target opponent loses life equal to its mana value. If it's an instant or sorcery card, you may cast it without paying its mana cost.

Nagas and Serpents you control are Snakes. (We'll errata this to be true.)
Snakes you control have daunt, deathtouch, and poisonous 2. (A creature with daunt can't be blocked by creatures with power 2 or less.)

Up to one target creature has base power and toughness 1/1 until end of turn. Up to one other target creature has base power and toughness 4/4 until end of turn. Then Hostile Takeover deals 3 damage to each creature.

Mutate
Flying, trample
Whenever this creature mutates, exile cards from the top of your library until you exile a nonland permanent card. Put that card onto the battlefield or into your hand.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
, , — Create a 3/3 black Wraith creature token with menace. The Ring tempts you.
For each opponent, gain control of up to one target creature that player controls until end of turn. Untap those creatures. They gain haste until end of turn. The Ring tempts you.

Eminence — Whenever another nontoken Wizard you control enters, if Inalla is in the command zone or on the battlefield, you may pay . If you do, create a token that's a copy of that Wizard. The token gains haste. Exile it at the beginning of the next end step.
Tap five untapped Wizards you control: Target player loses 7 life.

Untap each creature you control with a +1/+1 counter on it during each other player's untap step.

Flying
Federation — Faeries you control enter with an additional +1/+1 counter on them for each creature type among non-Borg creatures you already control.

Flying, haste
Whenever this creature deals combat damage to a player, you gain 1 life and draw a card.

When Jet enters, he deals damage equal to the number of creatures you control to target creature an opponent controls.
When Jet dies, put a +1/+1 counter on each of up to two target creatures.

Vigilance
When Katara enters, create a 1/1 white Ally creature token.
Waterbend : Creatures you control have base power and toughness X/X until end of turn. X can't be 0. Activate only during your turn.

When Kathril enters, put a flying counter on any creature you control if a creature card in your graveyard has flying. Repeat this process for first strike, double strike, deathtouch, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance. Then put a +1/+1 counter on Kathril for each counter put on a creature this way.

Whenever Kefka enters or attacks, each player discards a card. Then you draw a card for each card type among cards discarded this way.
: Each opponent sacrifices a permanent of their choice. Transform Kefka. Activate only as a sorcery.

Other Officers, Artificers, Doctors, Pilots, Scientists, and Spacecraft creatures you control get +2/+2.

Flying
Whenever Korvold enters or attacks, sacrifice another permanent.
Whenever you sacrifice a permanent, put a +1/+1 counter on Korvold and draw a card.

Whenever another creature dies, you may put X +1/+1 counters on Kresh, where X is that creature's power.

Vigilance, trample, haste
Whenever Liberty Prime attacks or blocks, sacrifice it unless you pay (two energy counters).
, , Sacrifice an artifact: You get and draw a card.

Flying, lifelink
Whenever another nontoken creature you control dies, return that card to its owner's hand at the beginning of the next end step.
If a creature an opponent controls would die, exile it instead.

Rather than pay for each previous time you've cast this spell from the command zone this game, pay 2 life that many times.
Flying, lifelink
Whenever a player casts a spell, they lose 2 life.

Double strike, vigilance, haste
Exhaust — , : Add three mana of any one color. (Activate each exhaust ability only once.)
Exhaust — , : Draw three cards.
Exhaust — , : Loot deals 3 damage to any target.

Lifelink
When this creature enters, search your library for a black card, a green card, and a blue card. Put those cards into your graveyard, then shuffle.

Maarika, Brutal Gladiator must be blocked if able.
As long as it's your turn, Maarika has indestructible.
Whenever Maarika deals damage to a creature, if that creature was dealt excess damage this turn, that creature's controller sacrifices a noncreature, nonland permanent.