So while the Prophets were set up from the start of the series, they weren't in the Dominion war story arc until this ep.
And, of course, the Prophets couldn't
have been included in the Dominion War story arc until the episode, because until that episode the wormhole was mined
, and the Dominion controlled the station
. How could the Prophets/Wormhole Aliens have been included in the war arc before
"Sacrifice of Angels"?