Explores and challenges offer kingdom specific stones, explores offering the “good” stones at a significantly improved rate. Because of the fact explores are generally superior to challenges in all ways I think something should be done to give challenges a niche.
In the game currently troops and traitstones are obtained from keys at a ratio of 3 to 1, in other words 75% troop 25% stone (this is data from over 21000 mixed chest types). My suggestion is to add troops at an inverted ratio, so roughly 75% stone 25% troop, to challenges limited to the kingdom’s troops. There are 7 challenges per kingdom and I’d make it so drops are limited by which you do
1st - All stones
2nd - Stones and Common
3rd - Stones and Common/Rare
4th - Stones and Common/Rare/UltraRare
5th - Stones and Common/Rare/UltraRare/Epic
6th - Stones and Common/Rare/UltraRare/Epic/Legendary
7th - Stones and Common/Rare/UltraRare/Epic/Legendary/Mythic
For example, say you do Adana on 3rd challenge. If your rarity indicates you would have gotten a Major stone, now you have a 75% chance of Major and a 25% chance of either Alchemist or Steam Turret (Adana’s 2 rares). If on that same challenge you would get an Arcane stone, you just get an Arcane since you aren’t on the 5th or higher to qualify for an Epic troop. Only troops currently in chests qualify.
This would give people that are looking for a specific troop a way to grind it. Need 5 more Sand Cobra to ascend it? Go farm Leonis Empire 2nd challenge. Want a Sylvanimora? Go farm Forest of Thorns on 6th or 7th, but it will take a while as it would be at roughly a quarter the rate of getting a celestial stone.
The reason that 1st challenge is just stones is that challenges are the single fastest way to farm minors, and I wouldn’t want that taken away.