Remove or greatly reduce the chance of monsters to get a wand of teleportation, on the basis that the vast majority of the zaps that monsters are given with these wands end up in the player’s hands, allowing them to bring a pile of them to the Astral Plane and use them to make that level significantly easier. If they do not generate in monster inventories, a full game might see about 3 or 4 wands appear on average.