There was nothing besides the cold and snow coming out from the opening. The tension between both sides was quickly dispersed and replaced by fear of being ambushed by the undead while having no power.
It would be easy to kill them all from the outside now they are stuck here, only sending the undead would already make dozens of them fall at the first moments of the battle. The bridge is huge, comporting hundreds of people right now, but there was not space to a dozen more, so a fight was simply impossible.
A few of them near the opening were forced to pass through it after some time, with everyone waiting to see if they would die. What didn't happen, it was a safe cave far away from the castle, but close enough for them to see the wreckage of what once was the safest and most powerful on earth.
