General Information Edit
There are five types of gems according to minion stats:
Besides type, gems also have tiers. Higher tier gems have higher stat increases (both min and max), but due to wide quality range a bad tier 6 gem can improve your minion less than a good tier 4 gem.
There are four total gems of three different tiers available for sale at a time: two of the current key tier (starting with 1), one key+2, and one key+3. The gem store is refreshed every time you reload the game or clear another floor.
Gem Slots Edit
Every minion has up to 4 slots where gems can be placed and removed safely.
There's usually 1 initial slot for baby form, 2 for evolved one, and 3 for fully grown-up minion. Minions with just 1 evolution (e.g. Ticub) are considered 2nd form, and have 2 initial gem slots. Minions who don't evolve are considered fully grown.
An additional free gem slot for all minions at once is unlocked when you click the invitation to visit the SoGood website.
Gem Tiers Table Edit
11 Tiers of gem quality are available. For each tier, a gem's stats ranges randomly between a minimum and maximum stat. It is currently unknown whether these ranges may be exceeded by combining gems. The table below lists the stat range for each tier.
Gathering Gems Edit
Gems may be purchased from the Gem Salesman at the end of every stage. The Gem Salesman's inventory refreshes whenever you re-enter the floor or load a saved game. Saving the game while standing at the Gem Salesman, then re-loading the game, is one way to shop for gems with high stat rolls.
After defeating the Undead Sage, random gem chests may be found in the dungeon.
Combining Gems EditSeal of Passion) you are able to use blacksmith's services in the Lobby to combine gems. Combination requires three gems of the same tier, and results in one gem of the next tier. The better quality are the component gems, the better is the resulting one. The resulting gem stats are equal to half the sum of the component gems.
Different gem types can be combined together, resulting in mixed type gems. Though this is possible, such gems are not very useful compared to specialized ones because you usually want to heavily adjust 1-2 stats.
Edit: The result formula is inaccurate; it would look like the resulting stat (for a specialized gem) is closer to the sum divided by ~2.5 (For a mixed gem, divide each separate stat by ~2.5). Further testing is being performed to figure out the real formula...