The Keeper of the Underground Knights' Arsenal gives tasks for collecting crystals. I'm at the one where we collect 35 red and blue each. Do we collect all in one CC battle or over multiple battles??

You can do that im multiple CC runs. The only one that you have to do in one CC run is 113 green quest.

where is that quest

mattyb Arsenal Keeper in Hell's Pass if you are magmar, Foothills if you're a human.