Looks like that obelisk was important after all. It was lighting up one of those globe switch doohickeys at the bottom of the hole, which was apparently keeping the door open. Just great.
Hey check it out. Every week we'll be revealing some new troll characters from Hiveswap until Act 2 is out. Follow the Troll Call here, and meet the first two here. Expect a few more surprises like this to drop in coming weeks.