Okay.
You start with a certain weapon, say a Rapier. You need Sharpstone (a enemy/crystal gecko drop) in order to upgrade to Raper +1, +2, etc. Once you get to about +4, you need some of the harder to find "large splinter of sharpstone" in addtion to the easier to find sharpstone splinters to continue upgrading your weapon. At +7 you need "chunk of sharpstone" which is even harder to find.
Once you reach certain weapon levels (like a +4 rapier, for example), your regular weapon can be upgraded into a special one (curved,sharp, etc). Those given upgrade paths use special ores for upgrading that are generally hard to find, and some give bonuses based on a certain skill or combination of skill levels.
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