One possible solution could be to make him panic (by kicking him enough or finding and casting Scare Monster / Holy Awe) and then offer peace. Or does that not work on uniques either?
You hit Andor Drakon, the ElDeR cHaOs GoD, and severely wound him.
The greater balor summons some help!
The ratling duelist disarms you. You drop your blessed Trident of the Red Rooster (+36, 6d12+18) [+12, +12]. It flies to the west.
Andor Drakon, the ElDeR cHaOs GoD, picks up the blessed Trident of the Red Rooster (+36, 6d12+18) [+12, +12].
Andor Drakon, the ElDeR cHaOs GoD, wields the blessed Trident of the Red Rooster (+36, 6d12+18) [+12, +12].