Overwhelming Stampede

Until end of turn, creatures you control gain trample and get +X/+X, where X is the greatest power among creatures you control.

Swamp

Relentless Rats

Relentless Rats gets +1/+1 for each other creature on the battlefield named Relentless Rats.
A deck can have any number of cards named Relentless Rats.

Golgari Guildgate

Golgari Guildgate enters tapped.
{T}: Add {B} or {G}.

Krosan Grip

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Destroy target artifact or enchantment.

Harmonize

Doubling Chant

For each creature you control, you may search your library for a creature card with the same name as that creature. Put those cards onto the battlefield, then shuffle.

Go for the Throat

Dark Ritual

Steely Resolve

As Steely Resolve enters, choose a creature type.
Creatures of the chosen type have shroud. (They can't be the targets of spells or abilities.)