Failed Fording

Return target nonland permanent to its owner's hand. If you control a Desert, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Outcaster Greenblade

When Outcaster Greenblade enters, search your library for a basic land card or a Desert card, reveal it, put it into your hand, then shuffle.
Outcaster Greenblade gets +1/+1 for each Desert you control.

Desert Warfare

Whenever you sacrifice a Desert and whenever a Desert card is put into your graveyard from your hand or library, put that card onto the battlefield under your control at the beginning of your next end step.
At the beginning of combat on your turn, if you control five or more Deserts, create that many 1/1 red, green, and white Sand Warrior creature tokens. They gain haste.

Cloudpost

Cloudpost enters tapped.
{T}: Add {C} for each Locus on the battlefield.

Sinuous Benthisaur

When Sinuous Benthisaur enters, look at the top X cards of your library, where X is the number of Caves you control plus the number of Cave cards in your graveyard. Put two of those cards into your hand and the rest on the bottom of your library in a random order.

Dune Chanter

Reach
Lands you control and land cards you own that aren't on the battlefield are Deserts in addition to their other types.
Lands you control have "{T}: Add one mana of any color."
{T}: Mill two cards. You gain 1 life for each land card milled this way.

Ramunap Hydra

Vigilance, reach, trample
Ramunap Hydra gets +1/+1 as long as you control a Desert.
Ramunap Hydra gets +1/+1 as long as there is a Desert card in your graveyard.