Contagion Clasp

When Contagion Clasp enters, put a -1/-1 counter on target creature.
{4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Sol Ring

Swamp

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Ziatora's Proving Ground

({T}: Add {B}, {R}, or {G}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Xira, the Golden Sting

Flying, haste
Whenever Xira attacks, put an egg counter on another target creature without an egg counter on it. When that creature dies, if it has an egg counter on it, draw a card and create a 1/1 black Insect creature token with flying.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Savage Lands

This land enters tapped.
{T}: Add {B}, {R}, or {G}.

Scute Swarm

Landfall — Whenever a land you control enters, create a 1/1 green Insect creature token. If you control six or more lands, create a token that's a copy of this creature instead.

Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

Mountain

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Parallel Lives

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Forest

Hornet Queen

Flying, deathtouch
When this creature enters, create four 1/1 green Insect creature tokens with flying and deathtouch.

Arcane Signet

Contagion Engine

When this artifact enters, put a -1/-1 counter on each creature target player controls.
{4}, {T}: Proliferate twice. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)