Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Serum Snare

Return target nonland permanent to its owner's hand. If that permanent had mana value 3 or less, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Slip Out the Back

Put a +1/+1 counter on target creature. It phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

Tekuthal, Inquiry Dominus

Flying
If you would proliferate, proliferate twice instead.
{1}{U/P}{U/P}, Remove three counters from among other artifacts, creatures, and planeswalkers you control: Put an indestructible counter on Tekuthal, Inquiry Dominus. ({U/P} can be paid with either {U} or 2 life.)

Splash Lasher

Offspring {1}{U} (You may pay an additional {1}{U} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
When this creature enters, tap up to one target creature and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Blighted Agent

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
Blighted Agent can't be blocked.

Atmosphere Surgeon

Whenever you cast a noncreature spell, put an oil counter on Atmosphere Surgeon.
Remove an oil counter from Atmosphere Surgeon: Target creature gains flying until end of turn. Activate only as a sorcery.

Ichor Synthesizer

Whenever you cast a noncreature spell, put an oil counter on Ichor Synthesizer.
As long as Ichor Synthesizer has four or more oil counters on it, it gets +2/+0 and can't be blocked.

Scroll of Isildur

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Gain control of up to one target artifact for as long as you control Scroll of Isildur. The Ring tempts you.
II — Tap up to two target creatures. Put a stun counter on each of them.
III — Draw a card for each tapped creature target opponent controls.

Staff of Compleation

{T}, Pay 1 life: Destroy target permanent you own.
{T}, Pay 2 life: Add one mana of any color.
{T}, Pay 3 life: Proliferate.
{T}, Pay 4 life: Draw a card.
{5}: Untap Staff of Compleation.

Reject Imperfection

Counter target spell. If that spell's mana value was 3 or less, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Trawler Drake

Flying
Trawler Drake enters with an oil counter on it.
Trawler Drake gets +1/+1 for each oil counter on it.
Whenever you cast a noncreature spell, put an oil counter on Trawler Drake.

Steady Progress

Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Draw a card.

Experimental Augury

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Referee Squad

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Vigilance
When Referee Squad enters, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Dreamtide Whale

Vanishing 2 (This creature enters with two time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Whenever a player casts their second spell each turn, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Mesmerizing Dose

Enchant creature
When Mesmerizing Dose enters, tap enchanted creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Enchanted creature doesn't untap during its controller's untap step.

Out Cold

This spell can't be countered. (This includes by the ward ability.)
Tap up to two target creatures and put a stun counter on each of them. Investigate. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Gitaxian Anatomist

When Gitaxian Anatomist enters, you may tap it. If you do, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Mercurial Spelldancer

Mercurial Spelldancer can't be blocked.
Whenever you cast a noncreature spell, put an oil counter on Mercurial Spelldancer.
Whenever Mercurial Spelldancer deals combat damage to a player, you may remove two oil counters from it. If you do, when you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.

Tezzeret's Gambit

({U/P} can be paid with either {U} or 2 life.)
Draw two cards, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Involuntary Cooldown

Tap up to two target artifacts and/or creatures. Put two stun counters on each of them. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Succumb to the Cold

Tap one or two target creatures an opponent controls. Put a stun counter on each of them. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Contentious Plan

Impede Momentum

Tap target creature and put three stun counters on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Serum Sovereign

Flying
Whenever you cast a noncreature spell, put an oil counter on Serum Sovereign.
{U}, Remove an oil counter from Serum Sovereign: Draw a card, then scry 2.

Flux Channeler

Whenever you cast a noncreature spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Cytoplast Manipulator

Graft 2 (This creature enters with two +1/+1 counters on it. Whenever another creature enters, you may move a +1/+1 counter from this creature onto it.)
{U}, {T}: Gain control of target creature with a +1/+1 counter on it for as long as Cytoplast Manipulator remains on the battlefield.

Prologue to Phyresis

Each opponent gets a poison counter.
Draw a card.

Wicked Slumber

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Tap up to two target creatures. Put a stun counter on either of them. Then put a stun counter on either of them. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Freeze in Place

Tap target creature an opponent controls and put three stun counters on it. Scry 2. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Gitaxian Raptor

Flying
Gitaxian Raptor enters with three oil counters on it.
Remove an oil counter from Gitaxian Raptor: Gitaxian Raptor gets +1/-1 until end of turn.

Inexorable Tide

Whenever you cast a spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Ichorplate Golem

Whenever a creature you control enters, if it has one or more oil counters on it, put an oil counter on it.
Creatures you control with oil counters on them get +1/+1.

Shackle Slinger

Whenever you cast your second spell each turn, choose target creature an opponent controls. If it's tapped, put a stun counter on it. Otherwise, tap it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Radstorm

Storm (When you cast this spell, copy it for each spell cast before it this turn.)
Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)