Players need certain hard-to-obtain traitstones badly. I propose a minigame in Khaziel to craft them.
Cost of entry: Gold, plus up to 10 traitstones (any color) deposited into a hopper. Rarity determines number of turns you’ll get: Minor = 0.5, major = 0.9, runic = 1.6, arcane = 3, celestial = 5; the total is rounded up.
Gameplay: You’re presented with a field of rocks of all six colors plus gray, and a limited number of turns like the treasure hunt. Also like the treasure hunt, you get turn bonuses for matches of 4 and 5. Matching rocks will reveal partially refined ore, and matching partial ore produces a minor traitstone–or for gray, a magic crystal. Any traitstones on the board at the end are yours to keep.
Fusing traitstones: A minor traitstone has 1 energy. Dragging 1 traitstone onto another of the same color will combine their energy; this is a free action. Getting a match of 3 or more the regular way will combine and give +1, but use a turn (unless it’s a 4 or 5 match). When they reach the next energy threshold they promote to the next level–except for runic and beyond, which don’t promote automatically. A major traitstone has N energy (N=10 would be an example); runic has either N^2 or some other number (e.g., maybe 50 instead of 100), and so on upward.
Crystals: These are pure energy, and can be fused or matched with other crystals or traitstones. Fusing a crystal with a traitstone causes the traitstone to gain the energy, and the crystal is destroyed; fusing two crystals will result in a more energetic crystal.
Making arcane stones: Runic stones that are ready to promote won’t do so immediately. You have to fuse two such stones together, but they can be any two colors. This will create an arcane traitstone. Arcanes can fuse with any single-color stone of either of their component colors, or with any other arcane stones. When fusing two arcanes, the one you dragged is the color combo that’s kept; when matching, it follows the same rules as the treasure hunt for whichever piece prevails (e.g., the one you dragged, or the middle one in a cascade).
Making celestial stones: Fusing any two arcane stones that are ready to promote will create a celestial traitstone. Any excess energy is lost.
Stone sacrifice: During gameplay, you can sacrifice traitstones you already have into another hopper, which gives you 1/3 of their energy. Then you can use the blast cannon to shoot that energy onto the board onto any piece you like–even a crystal, which would change it to a traitstone of that color. This does not use a turn.
Implementation goals: Costs and energy should be calibrated so that there’s a reasonable chance of getting a +1 level improvement over the average level of the 10 traitstones you initially put in. If the gold required is higher (e.g., 10,000), that chance should be pretty decent indeed.