The Greater Deep is an area located underneath the God Wars Dungeon, and is quite possibly the most dangerous place on Runescape. To get there, you must obtain a Divine key as an extremely rare drop from Commander Zilyana, K'ril Tsutsaroth, Kree'arra, Lord Shadowcore or General Graardor; then use it on the frozen door at the southern part of the Dungeon; this will open the door and lead to a chilly room with a frozen spiral staircase, walk down these stairs to access the Greater Deep.