I personally see a lot of potential in the mechanic. At a first glance, everything about it was extremely interesting. The idea of a deck master that can only be unlocked by playing a game within a game was a very creative concept, and the Mythron rarity brought about the appeal of exclusivity. It was natural that I was very excited for them.
But when they officially entered the meta by the time the expansion dropped, the problem was evident. Mythron decks were severely obstructing player interactions, where matches would just be a game of “who summons the Mythron first.” Strategy and gameplay skill became minimized while deckbuilding importance was maximized; a trend I personally don’t welcome.
To make matters worse, these Mythron minions are uncounterable. Cards like Notion, Hatefurnace, Underlord, and Strategos are overwhelmingly powerful. (As a Lyonar main, I used to be heavily biased towards Strategos, but I now know better. It may not be downright overpowered, but it’s definitely the strongest Lyonar archetype at the moment.) I’m not asking for their effects to be dispellable or removable, as that would take away from their appeal as a win-con, but I’m definitely asking for some adjustments to either their Trial or Destiny. No other minion in the entire history of Duelyst was able to entertain such a massive presence on the board by itself, and nothing should be this powerful even if the Trial needs preparation to complete.
Furthermore, the balance between Mythron minions is also very problematic. Cards like Ebon Ox or Oak are disastrously underpowered compared to others, as their Trials are difficult and their Destinies inconsistent. These cards make me feel like the difficulty of the Trial and the power of the Destiny are inversely proportional. Although I have no plan to ever play these cards, I would like a rework done so that they become playable.
To conclude, the Trial and Destiny mechanic is a great concept that was executed so poorly that it ultimately became unhealthy for the game. If I were to redesign them, I would make the Trials more interactive with opponents and synergetic with existing card archetypes. The Destinies should be nerfed overall, but obviously should be strong enough for the Trial to be worth it. There ought to be an equilibrium somewhere.