Katryx Blade sucks in terms of attack, its main use is Armor Breaking skill which is necessary for Lace fight, and is a permanent defense down otherwise. Don't dual wield them, use one alongside another weapon.
At the point I'm at in the game now, the combo I've been having Ryen wield is: "Golden Thunder Blade" in one hand and "Eagle" in the other.
I like the slight benefit I get from regular attacks now using the element Thunder while wielding "Golden Thunder Blade".
And the fully-completed "Eagle" is hilariously overpowered in terms of the magic attacks Ryen can launch against all opponents at once. I honestly don't see any reason at all to complete the "Summoning Blade" right now. Perhaps later on Ryen will need the meteor spell you get from giving that sword back. But until that time, I'm gonna keep wielding "Eagle" and leave the "Summoning Blade" quest unfinished.
I'm curious what weapon combos other people use for Ryen (and Sandra for that matter for those who regularly use Sandra as a combattant).