Tumblusen told you there were more and more Krall Scouts around the Observatory, and asked you to get rid of them. It seemed to indicate a serious problem though, so you reported the situation to General Telemachus, who ordered you to ask Mabangtah for help in scouting out the Kaidan Headquarters. You found an Abyss Gate in the Kaidan Headquarters while scouting, and reported back to a shocked Tumblusen.