Ok, so had a weird situation come up in a game last night.

An epic battle had been played during the plot phase

"Plot: After the dominance phase this round, there is an epic phase during which each player may initiate a single power challenge with normal claim. The winner of each challenge may draw three cards. (Place this card next to your plot deck until the end of this epic phase.)"

My opponent has out Rhaegar Targaryen

"Response: After Rhaegar Targaryen is killed, end the current round. Proceed to the next plot phase. Any player can trigger this response."

Ok, so I win a MIL challenge. He chooses Rhaegar to die. He triggers Rhaegar to end the round. What happens to the Epic Battle? Does it stay by the house card until the following round? We chose to discard it, it seemed like it made sense. But there was no dominance phase, so we weren't sure.

Since "epic battle events" create a new phase inside the current round, ending the round immediately will prevent all subsequent phases to take place, including the "epic phase".

It's in the FAQ:

(v1.0) Rhaegar Targaryen F82
When the round is brought to an end by
Rhaegar's ability, the current phase and all
phases remaining in the round are also considered
to end. If the round ends during a challenge,
that challenge ends without resolution.

So yes, the Epic Phase is considered to have ended (even though it never began). In fact all "at the end of the phase" effects and "until the end of the phase" durations are considered to have ended. This was actually specifically added to the FAQ to clarify that Epic Battle cards are discarded (even though their Epic Phase never happened) and that "gets -X STR until the end of the phase" effects still end, even though the end of the phase never technically happened.

Thanks, I should have looked it up in the FAQ first. My bad.