You may cast a spell with mana value 3 or less from among them without paying its mana cost
One thing worth noting is that Invasion of Zendikar has a subtype: Siege
Within those sets of inks are cards that are catered to specific play styles, so there are top cards in each ink type that perform extremely well
Solemn Simulacrum doesn't look like much at first glance, but the combination of his effects creates a large swing in your favor, netting an extra land, a smoothing of colored mana, an extra land play, and replacing the card when it dies
Its a mega-staple, and this is the best version to date
Manglehorn Manglehorn is a great way to slow down opposing artifact decks, which can be a very useful tool in a mono-green deck