Legendary Challenge Mode
Temple of Febe is the first encounter in Guild Wars 2 to introduce a Legendary Challenge Mode. When this is activated, the boss’ HP increases by about 24 million, reaching over 130 million HP, and several mechanics recieve additional buffs that make them much more difficult to manage.
Cerus LCM is extremely challenging, due to the tight damage check introduced by Cerus’ extra survivability, and the difficult healing check in the final phase. A successful clear of the LCM requires minimal errors in the entire fight, all the way up to the end.
If you’re aiming for the LCM, it is strongly recommended to first clear the normal CM. The mechanics are very similar, and building familiarity with them is extremely useful for progressing.
Embodiment Of Sin
EoS is the title run for Temple of Febe, requiring that players kill the Challenge Mode with all of Cerus’s aspects empowered. This is the hardest encounter in the game, much harder than LCM, and is usually faced with specialized builds and modified strategies.
Minas’ dedicated guide for the old version of the encounter can be found here.