Dark Sentinel Double

Legend has it that only one Dark Sentinel can emerge in each era.

He will become the king of his age!

What if two Dark Sentinels appear?

Tang Rui: Take him down!

Lu Hao: Take him down!

[Set in a Sentinel and Guide universe, but both protagonists are Dark Sentinels. Dark Sentinels can maintain their mental stability without Guides, so they are known as the kings among Sentinels. This is an adapted setting, not an original concept, and draws on reference materials and Sentinel-Guide settings found online.]

Theme: They are each other's salvation.