In Frontier you can only use cards newer than M15, which has the new type of frames. Bit like Modern but even more limited.
Read more:
https://mtg.gamepedia.com/Frontier
Frontier
Published
In Frontier you can only use cards newer than M15, which has the new type of frames. Bit like Modern but even more limited.
Read more:
https://mtg.gamepedia.com/Frontier
MTG blog 