This review goes over all the basic rules in a pretty succinct manner. They also https://www.youtube.com/watch?v=qeyECQD4NVA
But for the short short short version, each player has a deck of 25 cards (you can play with the pre-made decks or customize your own). You pick one card to be your "leader" which is the side of the card with a proper name and a special ability that extends to your entire army. The leader stands in the middle of a 3x3 grid that makes up your "unit".
After that point, the rest of the cards in your deck will be used as either heroes or orders. Heroes have different abilities depending on whether they are placed in the front, middle, or back row of your unit. An order is basically a big one-shot ability before discarding the card.
Both units will go back and forth, attacking, knocking out units, using abilities, clearing corpses (yep, you have to clear a corpse off your side before you can use a space on the board again) and repositioning themselves, all in an effort to knock out the opposing leader.
And thanks for the tips on where to hunt down sprites, Sticky!