TL;DR: Massive gem destroyers and exploders exist and are used widely by the players, please please realize that and take it into account before making new troops based on the new special gem mechanics.
Since the introduction of special gems, they are controversial in the community. Many players hate them, some like them. Triggering these new gems usually either grant effects (Lycantropy, Burning, Curse, Gargoyle), or give mana (Potion, WIldcard, Elemental star, Wish, Bomb) to troops.
There are two new kingdoms that are strongly based on special gems: Nexus with Elemental star, and Hellcrag with good/evil Gargoyal gems.
Many troops that have the ability to create / transform new gems and have the spells that are scaled with these new gems on board.
The problem of the mechanics of these new gems, in my opinion, is that they are by design neutral to both the player and the opponent, since they are created on the board and both parties can trigger them. This leads to the fact that those new troops that create new gems, many times are working for the opponent rather than the player.
If we look at all the new troops with special gems and try to find those who are considered useful, most of them can control the extra turn, such as Centuragon, Flaming Oni, Hatir & Skroll, Celestial Flask.
This is of course because if you can’t trigger those gems immediatly or control the turn, the opponent will trigger them and you will be defeated by yourself. It feels stupid, and it is stupid.
The worse part is that some troops’ spell are designed to scale with the number of special gems on board, which means if you want to ultilize their spell’s potential, you want more special gems on board. Now if you don’t have the ability to keep the turn, more special gems on board is equal to more disaster when the opponent trigger them. And if you want to trigger these gems asap, the scaling modifer is useless.
Let’s use Xenith as an example. Its spell creates Doomskulls with the number scaling with evil gargoyle gems on board, its trait creates evil gargoyle gems when matching 4/5. In my experience, it doesn’t feel safe to use his spell without at least 4 evil gargoyle gems, and if it fails to get an extra turn, you are doomed. And once I cleared the board with Doomskull explosion or something else, I need to wait for another 4 evil gargoyle gems to (kinda) safely cast him again. Meanwhile the opponent can cast thrall or leprechaun easily and put all status effect on me and let me wait longer for the gargoyle gems.
I was trying to test a good Xenith team and in the end, the most reliable way is just casting Chalcedony again and again and only use Xenith when you are absolutely sure, and once you cast it, you again use Chalcedony again and again to get enough gargoyle gems. I am tired of Chalcedony in the 3 weeks of Hellcrag. It’s a pity that so many troops are designed around gargoyle gems but the best way to play is with one troop that has nothing to do with gargoyle gem.
Xenith is still a better troop in those scenarios since it does have the potential to get extra turns. The Werestag needs more Lycantropy gems to safely cast and you have to pray the opponent don’t trigger those gems during the waiting time. Kalika’s damage is boosted by Elemental stars, which is a kind of gem that can be matched easily without gem destroyers, and she doesn’t have extra turn potential, so you either cast her without much damage boost, or cast and see the opponent get all mana. Same with Tourmaline. I’m not even talking about Sparkinator who creates 10 bomb gems and explode one random gem, it’s like you have 50/50 chance to benefite the opponent when casting a 22 mana cost mythic troop.
To be fair with the devs, I think they have realized this point somewhat and try to make special gems unmatchable with other normal gems, like the recent ones: wish gem, bomb gem and gargoyle gems. They are improving: Lycantropy is the worst since no matter being matched by you or the opponent it’s a loss for you, potions once being matched just keep looping, wildcards / elemantal stars can be easily matched, wish gem can be bad for both and bomb gem is kinda useless so who cares it’s triggered by whom.
But I want to remind them, who are probably testing the game with arena-like battles (no offense): Massive gem destroyers and exploders exist and are very commonly used, some of the best among them have very low rarity and easy to get: Leprechaun, Thrall, Mountain Crusher, etc. The opponent don’t need to match those special gems, they can easily trigger the whole board. There is still no room in most battles to let special gem numbers grow without the ability to control the turn.
Please take that into consideration when you design new troops and new gems. The introduction of new gems just make the ability to “control the turn” even more vital.
There are all the low rarity new troops that has a chance to create / convert few special gem in their trait or spell, only to be triggered by a leprechaun cast by the opponent. But the number of special gem involved is less, so the damage is less. But Mythics and Legendary troops that require or create more special gems, you gonna to be more careful. It takes longer to fill them mana and we expect a cast of their spells to be useful, not useless or harmful.