The .dec file is a widely used file type for Magic decks. It can be opened and edited using just about any text editor. In fact, it’s such a popular format, that even Magic Online will allow you to export your decks in the .dec format.
Here is a sample of what a .dec file looks like when you open it:
//Esper
2 Ætherling
3 Thassa, God of the Sea
3 Nightveil Specter
2 Ashiok, Nightmare Weaver
2 Elspeth, Sun’s Champion
3 Jace, Architect of Thought
2 Sphinx’s Revelation
3 Azorius Charm
3 Doom Blade
2 Far // Away
3 Hero’s Downfall
4 Supreme Verdict
2 Detention Sphere
3 Temple of Silence
4 Island
2 Plains
2 Swamp
3 Watery Grave
4 Temple of Deceit
4 Godless Shrine
4 Hallowed Fountain
SB: 2 Obzedat, Ghost Council
SB: 2 Glare of Heresy
SB: 3 Negate
SB: 2 Master of Waves
SB: 2 Celestial Flare
SB: 2 Thoughtseize
SB: 2 Fiendslayer Paladin
//Notes
You can add any notes about your deck here. They will be visible in Reliquary by loading the deck, and tapping the “Compose” button in the top-right corner of the Deck Box screen.
You can copy and paste that directly into any text editing program and save it as “deck.dec”. That file will then be able to be imported into Reliquary using Dropbox, Email, or iTunes File Share.