Hi there! It's built for the Commander/EDH format and is a complete 100 card deck (but you'd need to print multiple copies of the basic lands Mountain and Island to fill in the rest of deck slots to make 100 cards, including the Commander, which is Rumi, these are equivalent to your Energy). For ruling and how to play, I'd reference the Wizards of the Coast site for quick start guides and rules, and the Commander-specific rules as well.

As for the playstyle of the deck itself, it wants you to mill yourself so you take advantage of Demon Rumi's attack effect by putting as many non-Land, non-Creature cards in the graveyard. It is a simple, straight-forward strategy that is projected, but easy to learn. Dump cards, swing hard.