DoTA

Trying to enchant an item you can get four results.
1. Success
2. Failure
3. Blockage (can be released with special item)
4. Broken.

Success will result in +1 to items current grade (Ex.: +2 => +3).

You can fail to enchant at any grade it will result in item staying on same enchant grade and your "enchant item"+gold for enchant will be lost.

Armor and jewelry can be enchant to +4 without risk of breaking.
Weapons can be enchant to +9 without the risk of breaking.
After the values specified above there is a high risk of the item to be locked or broken.