Deck building

Build your decks. The app will keep track of them including the sideboard.
You can import/export the deck in .dec format.

Up to date MTG database

MTG card database is from Probably the best source to get MTG data.

"MTGJSON is an open-source project that catalogs all Magic: The Gathering cards in a portable format. A dedicated group of fans maintains and supplies data for a variety of projects and sites in the community."