Sentinel Hill arena opens its gates for champions and pretenders. While the event is active talk to arena master to start a chain of event quests that will reward you with useful items and also a handful of ash required to create a unique eternal helmet. A formula for this helmet can be bought from the famous blacksmith Broderick, who creates equipment for the invincible champions of the arena.
The quests are available from level 10 and don’t forget that you can teleport to the arena by accepting a quest from arena master’s assistant.
After you complete all the quests for the first time, they will become dailies, so you can take them again every day while the event is running.