I've been suggesting this for a while, but instead of just a "Knights" clan, make a Medieval clan. They could have been brought forward in time by accident by the Vortex. Also, instead of just making them standard Medieval people, they could make them trying to fit in. A modern day King Arthur is much more interesting than a standard one. Also, there are lots and lots of medieval characters to base characters off of. Just look at Disney! lol
As for a bonus, how about either "Protection: Attack" or "Support: -3 Opponent Attack Min. 6"?
The opposite of Frozn, some elemental fire clan with fire knights.paladins/priests/wizards/snakes/beasts anything!
It's bonus could be confidence: +2 power and +2 damage and it could be called say magma and its cards can mainly be based on pure power.
Maybe a clan that controls the weather? There could be one that controls earthquakes, meteors, lightning, temperature etc.
It's bonus could be courage: stop opp ability and bonus and it could be called Forecasts and their cards could be mainly based on its abilities, so they have bad stats but make up for it with their abilities.
And finally a clan of crazy scientists!
It could be called Experims and their cards could be based on their damage with attack and power manipulation from their ability.