Since there is already a pseudo targeted method in the Soulforge for troops (the summoning stones), and as many have pointed out, the pool of shiny troops is getting too big to make ii feasible for the average player to find ones they need, how about a shiny summoning recipe? 1 key plus souls plus something else (maybe jewels to match the mana of the selection pool) gives you a troop from a defined pool of 10 shiny troops that then rotates twice a week like the mythics. You might have to wait a while to see the troop you need, but you have now a 10% chance of getting the one you want. Maybe even 20 gold marks, since they are being drastically nerfed by removing the purchase of imperial deeds and books.