the trick is...
...To use the age-old adventurer's technique of tying up and gagging your horses and putting them in trees before you go dungeoneering - they'll be safe there, because not even the stupidest wandering monster expects to find a bound and gagged horse up a tree.
...To run a flock of sheep and assorted poultry through the dungeon ahead of the party to set off all the traps and keep the monsters occupied with something to eat while you grab their phat lewtz.
...and if that doesn't work, the trick is...
...To flood the dungeon with a Decanter of Endless Water in order to drown all the monsters then use your Ring of Water Breathing to do a Jacque Cousteau for the phat lewtz, whilst hoping that none of said monsters don't need to breath air.