Deathly Grimm {HP x Merlin}

Merlin had been told to find the 'Deathly Grimm' and they would help him with his mission. However, he didn't know what the 'Deathly Grimm' was or if he was supposed to trust it. Who names themselves the 'Deathly Grimm'? Then he gets told it's a Peverell, which doesn't help his opinion, aren't they associated with death or something?
Lady Josephine Potter arrives at Camelot to stay while her home is repaired after a battle they recently had. Lord Fleamont Potter, or King Peverell, had also advised Uther that the King of Camelot has no say in Jamison's suitors. When Lord Orion Black appears in hopes of gaining Josephine's hand, Merlin somehow knew he was going to be involved.
Just Merlin's luck, he's gotta hide his magic from two more people and hope they still help him, without him directly saying what he needs help with.

Orion Black x fem!James Potter (kinda) x ?????

*I don't know own BBC's Merlin or the Harry Potter series*