Polypiling is a technique involving clever manipulation of the wand of polymorph's mechanics to gain free items of varied value. Although it is definitely an abuse of the game's mechanics, it is not popularly considered an exploit, perhaps due to the random nature of the rewards.
Polypiling is a useful technique to fall back on if in desperate need of food, or as a chance to get lucky and gain some rare equipment early on.
First, you will need a wand of polymorph. They aren't so common, but you're pretty much ready to go the moment one falls into your grasp.
Second, there are some rules as to how a wand of polymorph works:
- It can only zap a distance of five tiles
- It can only polymorph up to five items in a stack on a single tile
- When (a)pplied, the wand will polymorph items in a 1 tile radius including the tile you are standing on
Finally, the technique:
- Collect stacks of junk items (e.g. stones, sticks, cans, unwanted equipment)
- Place the items in stacks of 5 in a straight line 5 tiles long (like in the image above)
- Zap your wand of polymorph in the direction of the stacks
- All items will be polymorphed into random items
- Repeat as necessary, replacing junk items if needed
- Make sure that any pets/allies nearby are commanded NOT to consume anything valuable. There is nothing worse than watching Kenny the puppy wolf down the Holy Banana of Oily Orpiv that just appeared.
- Kill anything hostile in the area, take your polypile to a monster-free zone like New Attnam, or lock yourself inside a room to keep out neutral/hostile NPC's.
- DO NOT break (apply) a WoP without having intrinsic PolyControl or a ring of Polymorph Control, or you will be turned into a random creature for a significant time. Even if you're in a safe area you may be unable to do anything but watch as a polymorphed mushroom as NPC's eat/wear the items you just polypiled.