Plains

Halo Hopper

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.)

Ornithopter

Resolute Reinforcements

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, create a 1/1 white Soldier creature token.

Knight-Errant of Eos

Convoke
When Knight-Errant of Eos enters, look at the top six cards of your library. You may reveal up to two creature cards with mana value X or less from among them, where X is the number of creatures that convoked Knight-Errant of Eos. Put the revealed cards into your hand, then shuffle.

Recruitment Officer

{3}{W}: Look at the top four cards of your library. You may reveal a creature card with mana value 3 or less from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Pride of Conquerors

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Creatures you control get +1/+1 until end of turn. If you have the city's blessing, those creatures get +2/+2 until end of turn instead.

Thraben Inspector

When Thraben Inspector enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Snubhorn Sentry

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Snubhorn Sentry gets +3/+0 as long as you have the city's blessing.

Venerated Loxodon

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.)
When Venerated Loxodon enters, put a +1/+1 counter on each creature that convoked it.

Monk of the Open Hand

Flurry of Blows — Whenever you cast your second spell each turn, put a +1/+1 counter on Monk of the Open Hand.

Shefet Dunes

{T}: Add {C}.
{T}, Pay 1 life: Add {W}.
{2}{W}{W}, {T}, Sacrifice a Desert: Creatures you control get +1/+1 until end of turn. Activate only as a sorcery.

Clarion Spirit

Whenever you cast your second spell each turn, create a 1/1 white Spirit creature token with flying.