Upgrading/Reinforcing

In DFO you can upgrade your weapons and armor to enhance it's abilities.

From +1 to +6 armor grants an additional percentage of damage reduced, weapons grant bonus attack power that bypasses defenses.
From +7 and higher, armor will provide a flat damage reduction of 1 and higher. Weapons start o increase the additional damage by larger amounts.

The problem is that you can fail upgrading, and it's pretty expensive to start with. If that weren't pain enough fron +1-+7 failing an upgrade will lower the level by one. +8 - +10 a fail will cause the item to drop back down to level 0. From +10 and higher the item will be DESTROYED upon a failure.

The bonuses for having a +11 +12 or +13 item are pretty impressive, but the risks to get one are very high monetarily. You can also buy items from other players that are already highly upgraded, or you can get them out of item pots, but it's rare.