Discover Blades of Persia! A swirling sand tornado brings forth the Prince of Persia to Heathmoor. The Prince had to use his mystical dagger to change his destiny and survive. Yet meddling with time would have dark consequences for his stranded soul...

He brings an army of sand creatures in his wake for a special limited-time game mode, Ruler of Time, which tasks heroes to fight and defeat him and his sand creature minions in a variation of the Harbor Dominion map. During the match, the Prince will periodically emerge from a sand tornado and seek to destroy any heroes in his way with the legendary Dagger of Time.

In addition to the special mode, For Honor will receive Prince of Persia–themed changes including revamped in-game menus with new visuals and music from the Prince of Persia universe. The event also introduces a variety of themed customization items. As part of the free event pass, players will have access to 30 tiers of Prince of Persia–inspired gear and loot. 

There is even more details to discover, including patches to the game, so I suggest you hit off the patch notes to learn all about it.