Journey into Northrend to the Wyrmrest Temple and face Halion and his minions within the Ruby Sanctum on January 11 at 3:00 p.m. PST (23:00 GMT). You can currently test the raid on the PTR until 12/21.
Gather your allies and make plans to heed the call of the red dragonflight in their time of need.
Source: worldofwarcraft.com