Thought about this from The Red Wedding V Red Wedding thread.

"Return" can be saved from, while "place" can not?

i. e. You can save from Game of Cyvasse, but not Shield Islands Dromon.

mdc273 said:

You can discard a duplicate to save from any effect that removes it from play(except for when it has "cannot be saved" or it is during the "end of phase" framework).

You can only use a "save" effect against what is says it saves from.

So if the effect says "save a character from being killed," you can only use it against an effect that says "kill a character." It is worthless against "discard," "place in the dead pile," "return to the dead pile," "put on the top of your deck," etc.

Duplicates, however, are specifically defined as being able to save the character from being removed from play by any effect. So it doesn't matter what the text on the card says. If it would start "in play" and end up "not in play," a dupe can interrupt and save (unless specifically prevented).

So then if a there is a card with a dupe from River Raid (don't ask how), then that card can be saved from being returned to the discard?

mdc273 said:

No because you cannot trigger Responses during the End of Phase framework. River Raid has a character returned to the owner's discard pile at the end of the phase.

Bomb is correct. In theory, a dupe could save a unique card from being "returned" to the discard pile, but since there are no Responses during an end-of-phase framework action window, it cannot happen in a practical sense for River Raid.