Daily story missions are unlocked when your character reaches the level cap at level 30. These daily mission will mean replaying Main Missions on a high difficulty level. In each 24 hour period there will be 3 available missions highlighted in your map as dailies to complete.
Completing the missions will reward you with high level gear (specialized or high end) and 15 Phoenix Credits each for a total available of 45 a day. These can be saved up and spent for more high level items at the special Vendors.
We recommend taking a friend or a team on these missions as the level 30 enemies will be both armoured and aggressive and prove quite a challenge.