Re:What else are these cards good for?
Well.. you can use it to play a Titan:The arena clone.
Titan: The arena have 8 monsters and each monster have cards numbered from 0 to 10. You can use the strength 12 card as the main monster and 10-0 as the normal action/battle cards.
Of course playing it with Gargon means you wont have the spectators and also you will have 2 less monster than in the real Titan: The arena box.
All in all, I think it will be good enough to play