Roar of the Olozonians

When Roar of the Olozonians enters the battlefield,
look at the top X cards of your library. You may
reveal any number of Legendary Creature cards with total mana value X or less and put it onto the battlefield.
Whenever a legendary creature with Unite you
control would leave the battlefield, instead exile it
with a unite counter on it, then create three 1/1
human soldier with first strike. Draw a card.
You may cast Legendary creature spells with unite counters on it from exile.