Sliver Legion

All Sliver creatures get +1/+1 for each other Sliver on the battlefield.

Boros Garrison

Boros Garrison enters tapped.
When Boros Garrison enters, return a land you control to its owner's hand.
{T}: Add {R}{W}.

Gruul Turf enters tapped.
When Gruul Turf enters, return a land you control to its owner's hand.
{T}: Add {R}{G}.

Enchant creature
Enchanted creature can't attack or block.

Rakdos Carnarium enters tapped.
When Rakdos Carnarium enters, return a land you control to its owner's hand.
{T}: Add {B}{R}.

Selesnya Sanctuary enters tapped.
When Selesnya Sanctuary enters, return a land you control to its owner's hand.
{T}: Add {G}{W}.

When Dromar's Cavern enters, sacrifice it unless you return a non-Lair land you control to its owner's hand.
{T}: Add {W}, {U}, or {B}.

Equipped creature gets +3/+3.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Enchant creature
Enchanted creature gets +X/+X, where X is the number of creature cards in all graveyards.

Dimir Aqueduct enters tapped.
When Dimir Aqueduct enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.