“A brother will murder a brother” = Mordred killing Arthur. The knights are the Brotherhood; as a knight, Mordred will be Arthur’s sworn brother.
The Arthur/Odin confrontation was perfect ok

9 GIFs: Merlin saying “Arthur”
↳ companion to Arthur saying “Merlin” 

Merlin fanfic: “Second Sight” by tonightless

Summary: Arthur Pendragon received Morgana’s gifts instead of her, but does not realise their significance until his nightmares show him what he can become. With Uther’s sins revealed and his prejudice as strong as ever, can Arthur resist the lure of corruption? Or will he stray onto the second path of Albion, and forsake his destiny as the Once and Future King in order to have his revenge? AU.

Set: S1E13 (Le Morte D’Arthur) and onwards

Rating: T

Pairings: All will be present, though platonic Arthur/Merlin, Arthur/Morgana, Arthur/Uther and Arthur/Gwen are explored the most.

Read? 

(Source: tonightless)