Legendary refers to post-Update 29 end game contents, just like what pre-Update 14/MotU "Epic" referred to. Quests that are CR 31 on Normal difficulty is considered "Legendary". I.E. A level 29 quest on Elite, and level 30 quest on Hard (CR 31) is not considered Legendary.
Some item effects, such as Mortal Fear, work differently in this quest setting (Legendary Ward). Old Raid Timer Bypass Hourglass does not work on legendary raids.
As of Update 36 Patch 3, Reaper XP is now doubled for dungeons with a base CR of 30 or higher.
| Originally Posted by Cordovan (Contribs • Message • Email • Cordovan)
| We are planning to use the term Legendary to denote new quests, raids, and adventure areas that are CR31+, in the same way 1-20 is Heroic and 21-30 is Epic. The main difference being that in discussing Heroic/Epic, we are talking about both content and character levels, while in Legendary we're talking about content.