Fusing and transforming gems
You can fuse gems and transform them into Precious Dust in the Workshop.
Fusing allows you to create one gem of a higher class from four identical gems. For example, 4 Simple Opals = 1 Usual Opal.
To increase the gem class, go to the Fusing tab of the Workshop, select the gem you need, and hit the "Fuse" button. The number of gems used for fusing can be altered with the slider.
If you want to create several gems at once, use the multifusing function — it fuses eight or more identical gems.
Gems are fused for time and Silver, or instantly for Gold. The cost and duration of the fusing process depend on the class and the number of gems, as well as on the Workshop level. The higher the resulting gem's class, the more expensive the process. You can reduce the gem fusing time by using boosts.
If there are less than five minutes left until the end of fusing, the "Boost" button is replaced with the purple "Free" button. Hitting this will finish the process. The free autocomplete time can be increased if you have VIP status activated or have certain bonuses. Please note: some VIP status bonuses allow you to fuse gems instantly. When using multifusing, the autocomplete time is added together.
If you have less than four identical gems, then empty slots are highlighted red. This means that fusing is currently unavailable.
Upgraded Legendary gems
To obtain Legendary gems of levels I, II, and III, you will need to fuse different quantities of various gems.
For example, to obtain an Opal of Legendary I level, you will need to fuse a Legendary Opal with stacks of several other types of gems.
Upgraded Legendary gems can be fused over time without you having to spend any Silver. Alternatively, they can be fused instantly, either in exchange for Gold or, at certain VIP levels, without the need to spend any Gold at all.
As distinct from gems of lower classes, upgraded Legendary gems and Celestial gems grant several bonuses.
To extract these gems from pieces of equipment, you will need the Legendary Diamond Knife.
Celestial gems
Celestial gems are special gems that each grant four military bonuses. They don't have any classes or levels, and you cannot receive them as a reward or find them as drops — you can only create them by using specific quantities of various gems, including upgraded Legendary ones.
Celestial gems are always displayed in the Cache tab if you have at least one regular gem of any class. The icons of Celestial gems that you haven't yet obtained are grayed out.
Selecting the icon will open a window in which you will be able to create a Celestial gem if you have the required gems.
Celestial gems can be fused over time without you having to spend any Silver. Alternatively, they can be fused instantly, either in exchange for Gold or, at certain VIP levels, without the need to spend any Gold at all.
To extract these gems from pieces of equipment, you will need the Legendary Diamond Knife.
Transforming gems
In the Workshop, you can transform Legendary gems of all levels and Celestial gems into Precious Dust. The latter is required in order to build and upgrade Clan buildings, learn Knowledge of a certain kind in the Shamans' Residence, activate Siege status in the Stronghold, and to craft, upgrade, and set traps.
To transform a gem into Precious Dust, open the Cache tab in the Workshop and select a Legendary or Celestial gem. In the window that opens, go to the Transformation tab, choose the number of gems, and hit the "Transform" button.
Read more about this in the Clan Stronghold section.