Therris, The Wanderer

Whenever Therris, The Wanderer attacks, reveal
the top X cards of your library and put each
creature revealed this way onto the battlefield
tapped and attacking, where X is the number of deserts you control. Shuffle those creatures into
your library at the end of combat.
Whenever a nomad creature enters the battlefield
under your control it explores. If a desert is
revealed put two +1/+1 counters on it instead.