Terror keys were damn near the only keys I could get and in abundance. Just teleport to Countess, slay her, new game. I couldn't get Keys of Destruction b/c Nihlathak's corpse-explosion was too OP for my 5k HP druid. Countess was by far the easiest to get to. Hell, I had her drop two in one run twice. Make sure your crap filter isn't filtering them? Summoner is a little stingy, tho. Plus side of doing countess runs is that she drops runes. They may suck, but they can be cubed. I've seen her drop Ists twice. After an amount of runs you should have more than just keys to consider a reward.