Craft Affect

How are the random mods generated?
It's complicated. Basically you want to use the highest level items you have in the recipe, and have your highest level character actually create it.

The game actually takes into account the Clvl of the character doing the crafting, and the qlvl (Quality Level) of the item, which is determined by which monster dropped the item, or which level character spawned the item if it was bought from an NPC or gambled. See our Item Generation page for more details on Ilvl and everything else.

If you are looking to craft something, save one you find from a very high level monster on hell, and use your highest level character.