You gain Crafting ranks every level equal to half (rounded up) of your Proficiency Bonus, and you may have a maximum rank of twice your Character Level in any discipline (up to rank 20).
You may also gain one tenth of a rank for each unique item you craft. A 'unique item' meaning an item (or effect on an item) with special properties unique to the item. A rank 3 dagger has different properties (higher damage), compared to a rank 2 dagger, and is therefore unique. A rank 2 rune carved into a dagger has a different number of uses than a rank 1 rune carved into the same dagger, and is therefore unique. The same rank 2 rune carved into a rank 1 and rank 2 dagger are NOT unique, however, as even though the resulting dagger is unique, the effects generated at each step are not.
Once you have gained a full rank in this manner, you are incapable of gaining more partial ranks until you have passed a 'Certification Test'. This test involves successfully crafting an item one rank higher than your new rank. Ranks gained through level up are assumed you have completed this test.
If you choose one of your Crafting skills as your Expertise, additionally add half your Crafting rank (rounded up) when rolling the check.
In general you can decrease the time to complete an item by increasing the DC, at a rate of 1 DC increased per 1 hour of crafting time decreased, to a minimum of 1 hour.
There are 6 custom crafting disciplines in Sarsei, which should cover all things players may wish to craft:
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