My guess would've been the Golden Stallion of Ali Baba, due to the production defect encountered in the Throne Room.
And Ed, DON'T tell me that there was no production defect in this episode, because I have EVIDENCE to PROVE IT!!!
Here is my (quite drawn-out) evidence of there being a production defect during that run:
If you all remember, when the second runner re-entered the Throne room she stepped onto a box on the floor attached to the rotating wall, opening the door to the Swamp. This box is a actuating control platform, that when stepped on allowed access to the Swamp when using the Throne wasn't an option. The Guard stepped on the control platform behind the Throne when he entered through the double doors, and it is my hypothesis that this action of the guard stepping on the platform "gummed up" the system, disallowing access to the Swamp AT THAT TIME. But when the second runner stepped on the platform, the "lock" to the Swamp triggered and the door opened. It's ALSO my hypothesis that this incident led to the Season 2 Throne Room Guard emerging from the camera-left side of the room RATHER THAN the double doors, because the production staff learned the hard way that using the double doors was impractical with that room's layout. The production numbers that you all know from the in-order airing of Legends episodes on GaS confirms this second theory. And one thing that does support my second hypothesis is the fact that this episode was the only one of the 2nd Season where the Throne Room guard emerged from the double doors.