[Taqwus]

If you're too impatient for the dominion kill --

Black Bow of Botulf helps (guaranteed feeblemind if it hits, and a feebleminded Sphinx is of little threat unless its items attack). Staff of Kurgi works too, but that's Cons 8.

AN/AP afterwards (Gate Cleaver is a nasty case; and recall that fire is generally AP, while lightning is AN), or very heavy-damage attacks (Gifts from Heaven being one example). Feeblemind also hurts MR, if memory serves, which gives you a better chance via Soul Slay and similar spells.

Spam horror-marking and let the horrors do it.