The first test works great, although the sharp flash stuns you as well, you're confident you could make at least ten of them. Best to mention that to all of your little spawnlings so they know to stay out of any room with this, at least until it goes off. The location triggers don't seem to work that well, at least not at first. Detecting motion, or an interruption of light patterns seems easy enough, like the type of spell and the triggering mechanism work best when they're the same element and doesn't really add to the cost. The rest of the triggers seem to fall apart as you try to build them, but it feels like it's out of your range rather than something fundamentally impossible. Your attempt at the door opening trap seems to work the best, as the sharp change from no light to a sudden flare seems to work flawlessly, whereas the motion or 'shade ratio' triggers seem a bit more finicky, with one in five not going off right.
Placing two spell crystals next to each other makes them... echo a bit, and they don't seem to be working quite as well. They also don't feed properly as you try to feed just a bit of mana to the one that's been fired, but the other tries to slurp the mana up too, much of it 'spilling' over the top and seeming to disappear back into the dungeon. There's nothing intrinsically broken about it, and your plan to booby trap your magic crystals seems like it would work, it would just take twice as long for the main one to recharge and be slightly wasteful. So far, you haven't taxed your new supply of mana too much, but if you want to keep some magic for yourself, you'll need to limit yourself to ten of these, or three pairs if you're going to place them as double traps and you plan on recharging them on the fly without having to go out and recharge them manually. You can save some serious magical energy doing that, but you'll constantly have to expose yourself or Velvet, and you'll leave tracks.