The Thing About Angrist
Mentioned this in a comment the other day and I think it deserves its own post; I think Beren and Luthien's quest for the Silmaril happens on the "Eru works in mysterious ways" level to give Celegorm and Curufin their chances at redemption.
There are pretty big Celegorm and Curufin shaped holes in the questing party – the quest cannot and does not succeed without the Hound of Celegorm and the Knife of Curufin. One entity from each brother, one spot for each of them.
Let's look at how the interactions between Beren and Luthien and Celegorm and Curufin go.
First, Beren approaches Finrod about the quest. Celegorm recounts his oath and essentially threatens a second Kinslaying. "so now dark fear and brooding ire he cast on them, foreboding war of friend with friend [...] or haply battle, ruin, and woe in Doriath where great Thingol reigned, if Fëanor's fatal jewel he gained." {186O-187O}
The thought of, like, going with him to win back the Silmarils themselves does not seem to enter their minds. This can be forgiven at this stage, as it still seems like a suicide mission.
Later, then, Luthien comes to Nargothrond. In the Lay, we get a little aside with Curufin, where he tells Celegorm to go hunting to see if they can find news of Finrod and that, obviously, if he has a Silmaril, it would be theirs to claim – clearly the idea of the quest succeeding is no longer wholly absurd. Luthien finds Celegorm in the woods and gives him specific, actionable information about the quest.
Celegorm and Curufin, instead of taking the chance to reclaim a Silmaril, choose to imprison her instead. "Orodreth knew the purpose dark they would pursue: King Felagund to leave to die, and with King Thingol's blood ally by force or treaty." {25OO}
We should not delude ourselves into thinking this is not a rape threat. In the Lay, it's Curufin who tries to "marry" Luthien, but it changes to Celegorm in later versions, which I think is stronger because it's Celegorm who faces the punishment: Huan, his tool for the the accomplishment of his redemption quest abandons him, because he has refused the redemption.
Still, Huan returns to Celegorm's side and, though the brothers are cast out of Nargothrond, they are given the final chance at redemption when they come across Beren and Luthien in the wild for their third encounter with the questers.
They, uh, they aren't nice about it. They try to kidnap Luthien and murder Beren several times and thus close the door on their own redemption: Huan leaves Celegorm for good and Beren takes Angrist as a prize after defeating Curufin.
The rest of the quest unfolds as you know until Beren and Luthien are at the crown of Morgoth
>To move that helm of iron vast
no strength he found, and thence aghast
he strove with fingers mad to wrest
the guerdon of their hopeless quest,
'till in his heart there fell the thought
of that cold morn whereon he fought
with Curufin; then from his belt
the sheathless knife he drew, and knelt,
and tried its hard edge, bitter-cold
Curufin's knife, Celegorm's hound.
Beren tries for a second Silmaril and Angrist shatters as fate has not given for him to claim this one.
So, discussion question for the class: If Celegorm and Curufin had come on the quest as other interested parties, presumably on the agreement that Beren could show Thingol the Silmaril in his hand and then give it to one of the Feanorians because he's a rules lawyer who doesn't terribly care about the Silmarils outside of them being his bride price, would Angrist still have broken?
Tolkien speaks loudly of fate, but not the exclusion of choice. Celegorm and Curufin chose to be angry at the idea that someone else might ever touch a Silmaril rather than take the gift wrapped chance to fulfill their own Oath. Fate filled in their spots in the quest, but couldn't save them from the consequences of their own wrath and jealousy.