I'm not too into the lore and flavour components of card development, but I've been thinking of a potentially interesting mechanic, especially in EFC.
The idea is that you have a conditional activation based on the star count of the opposing card. For instance, the "Bravery:" keyword might refer to an ability that only activates against 4 or 5 star cards, and "Domination:" against 2 or 3 star cards.
Seemingly, this would allow for more precise balance tweaking or for addressing certain parts of the meta. You might have a 5* card that is less vulnerable to equalizer by giving it a Domination: Attack Mod ability, or a strong stat-line 5* card with Domination: +Life that would discourage the use of a low-star damage reducer or other non-pilling strategy. On the other hand, a 3* 8/4 Bravery: Cancel Power/Damage Mod may be a way to balance a card like $Pandora without having to rely on subpar statlines (e.g. 7/4). Alternatively, Bravery based damage reducers with decent stat-lines (e.g. a 7/4 Bravery: +3 Life) may lead to interesting bluffs or match progressions.
The downside is that these mechanics only work in a healthy way in a game-mode in which there is a balance of high- and low-star cards, like EFC or T1. In higher-star formats, Bravery: abilities may prove too meta-defining. That being said, it seems that the dev team are quite willing to print game-mode specific cards, so the occasional ban doesn't seem like a significant downside.
Sorry, 8/4 might've been too much for a 3* card, maybe 8/3 or 7/4.
Langren is great, I just bought it and I'm surprised by the new clan Volkan and their own Lizbeth 2.0.
Nonetheless, I really hope for another solid DR card in Piranas (I really find it enjoyable to win at an EFC by only 1 life)
Your idea is quite good, and if I may add, like killshot, an ability that activates at an odd or even number difference in power. Time in tourneys is especially crucial in decision making since you only have a limited number of it. This way it can challenge both parties since they have to consider the denomination of both cards whilst in a time constricted situation.