In regards to "typing" the cards - maybe iconify the large card family - like "location"/"creature"/"resource" - and then keep the hidden subtypes - like "slave"/"fogbeing"/etc. That way you can still keep the mystery while letting the player know generally where the card could and could not go?
Also - yeah, tooltip hovers will help a lot. I kinda didn't understand what the skill icons meant. Didn't stop me really, but it would've been nice to know what the "gas mask" icon meant.