.... get an invisibility scroll. Combined with a water walk spell (or better potions of water breathing) at least somebody should survive to get that part. Some save/reload before opening the chest should get everybody back alive. At that level it should be possible to kill the sprites. The covards method (get the attention of one at a time and shoot at it while running backwards) and possibly wands helps, and this is why potions are recommended, for some reason it is always the gal/guy who casts water walk that becomes unconscious first.
