How to upgrade my Cloak of Invisibility?

[Sythia]

So I found myself with a Cloak of +1 Invisibility, which was pretty cool, and I read that these can be upgraded to +2 and +3. However, I'm not sure how to actually do the upgrade.

I found myself with a Skill Stone, a Scroll of Enchantment, and a second Air sigil, and I tried using all three - using the Skill Stone on the Cloak did nothing, and I couldn't exit from the upgrade interface, so I ended up upgrading a ring. Using the second Air sigil with the Cloak in a forge did nothing - the two items simply appeared again after I clicked on the Forge button. And using the Scroll of Enchantment did nothing - it appears to have been wasted in the attempt.

That character is dead now, but for future reference, how am I supposed to upgrade my Cloak of Invisibility to +2 and +3 status?

[Tokmol]

There's always a chance that the wiki/spreadsheet is wrong and that it CAN'T actually be upgraded. Heck, the spreadsheet doesn't list the "seeking" enchantment for bows that makes the arrows homing and ignores armor.. but I've gotten one on my last 2 runs.

The enchant scroll should've worked if it was updgradeable though. Enchant scrolls are essentially skill stones that work on more stuff.

For reference, skill stones only work on items that solely modify skills you can find on your character sheet. If it doesn't affect your character sheet, or it does something else in addition to adding to your stats, the skill stone won't work. Strength, speed, perception, stealth, etc.

Ring of perception+1 that just adds to your perception? the skill stone will work.
Ring of light+1 that adds to your perception and also adds a light source? not gonna work.. but an enchant scroll WILL.

For sigils.. adding a sigil to an already magical item will only change its effect if a combination for it exists. It'll never improve on the same effect by increasing the number attached to it.

TLDR; It's definitely either enchant scroll, or the wiki is wrong. I might confirm later.

[Tokmol]

Yep. Either it was changed later, or the spreadsheet's just wrong. The invis cloak CAN'T be enhanced.

For items that can't be enhanced, the enchant scroll only serves to recharge the item instead. That's why the scroll still got used up.

[Sythia]

Ah well! I haven't gotten it again, but that's good to know at least. Thanks for checking on that!