General

@NoobHaxor

Thanks for clarifying. I did not know this.

[b]OLD[/b]
Basic Potential Slot Carver: 5% chance, 100% boom
Intermediate Potential Slot Carver: 10% chance, 100% boom
Advanced Potential Slot Carver: 10% chance, no boom

Since Sengoku Patch or something it got changed into the following stats:
[b]NEW[/b]
Basic Potential Slot Carver: 20% chance, no boom
Intermediate Potential Slot Carver: 40% chance, no boom
Advanced Potential Slot Carver: 60% chance, 100% boom

To bad I didn't collect many on my characters. I dropped most of them I had because I lacked slots. I do have a few left. If they were tradeable or moveable through storage I would have saved them.

So the Basic and Intermediate Potential Slot Carvers are good compared to the Advanced version...

[quote=puretppc]@janny1993: Really?

This says that it will [url=http://i.imgur.com/Hmu4ASF.jpg]boom[/url]

Used to be 10% no boom lol.[/quote]

Oh is that so, I just got this from a monster recently:
http://snag.gy/5xgbH.jpg

And it says no boom, so I assumed the others must be the same. I guess I was wrong.
If you want a more accurate answer though, you can always ask @Hualicious, she has a lot of information, big and small alike

@janny1993: Really?

This says that it will [url=http://i.imgur.com/Hmu4ASF.jpg]boom[/url]

Used to be 10% no boom lol.

@puretppc: they just recently changed the carvers so that they don't destroy upon failure anymore, they also increased the chances of success.

All boss should drop them, at a very low rate..

[url=http://maplestory.nexon.net/guides/game-play/systems/00FIj/equipment-upgrading-101-potentials#bonus]Taken from this guide[/url]
"Bonus Potential (sometimes called Additional Potential in-game) is an extra Potential system that allows for up to two Bonus Potential Lines to be added to an item completely separate from its existing Potential. Bonus Potential can only be added to items that already have regular Potential, and it is added with a different set of items called Slot Carvers. Just like regular Potential, Bonus Potential can be reset with a type of Miracle Cube called a Carved Slot Miracle Cube. It also has tiers, just like regular Potential, which correspond to better stats and effects the higher the tier."

Bonus Potential items:
[b]Basic Potential Slot Carver:[/b] Has a 5% chance to add 1 line of Bonus Potential to an item. If it fails, has a 100% chance to destroy the item. Can only be used on items with regular Potential. Untradeable; drops randomly from monsters.
[b]Intermediate Potential Slot Carver:[/b] Has a 10% chance to add 1 line of Bonus Potential to an item. If it fails, has a 100% chance to destroy the item. Can only be used on items with regular Potential. Untradeable; drops randomly from monsters.
[b]Advanced Potential Slot Carver:[/b] Has a 10% chance to add 1 line of Bonus Potential to an item. If it fails, does not destroy the item. Can only be used on items with regular Potential. An untradeable version drops randomly from boss monsters. A tradeable version can be obtained from the Gachapierrot.
[b]Superior Potential Slot Carver:[/b] Has a 20% chance to add 1 line of Bonus Potential to an item. If it fails, does not destroy the item. Can only be used on items with regular Potential. Tradeable; can be obtained from the Gachapierrot.
[b]Silver Potential Slot Carver:[/b] Has an 50% chance to add 1 line of Bonus Potential to an item. If an item already has 1 line, has a 25% chance to add a second line of Bonus Potential. If it fails, does not destroy the item. Can only be used on items with regular Potential. Only sold in the Cash Shop during special promotions
[b]Golden Potential Slot Carver:[/b] Has an 80% chance to add 1 line of Bonus Potential to an item. If an item already has 1 line, has a 40% chance to add a second line of Bonus Potential. If it fails, does not destroy the item. Can only be used on items with regular Potential. Only sold in the Cash Shop during special promotions.
[b]Carved Slot Miracle Cube:[/b] Resets Bonus Potentials on equipment. Carved Slot Miracle Cubes are only sold in the Cash Shop during special promotions.

*Only Basic and Intermediate carvers will destroy your item upon failure.
*Only basic, intermediate, and advance carvers drop from mobs; advance from bosses.
*Superior carvers may be bought from other players in FM (Expensive).
*When fusing 2 items with bonus potential, the new item has a high chance (90%) of coming with bonus potential. So if you fuse 2 items with potential AND bonus potential, the new item will have a high chance of coming with both instead of one.

@janny1993: Do those carvers like destroy items upon failure? Also, do easy bosses like Zakum or HT drop those?

You use slot carver dropped by boss monster to get a bonus potential.
You can upgrade bonus potential with a special cube that's only sold every once in a while in the cash shop similar to shielding ward/guardian scroll/etc...

There was a cash shop sale which sells special bonus potential scroll which allows you to reveal 3 lines of bonus potential an equipment without a bonus potential.
You can add more line of bonus potential with some special carver, which I forgot the names of.

its essentially another 3 lines of potential and you can cube it when nexon releases the cubes for it again which seems to be once a month and you should be able to use a pot scroll to get reg potential