First thing first is to test triggering and targeting system, so I place a spell into the crystal that just sprays lights in a specific direction. Simple tests would be location-based triggers, distance from crystal, or a sound based one(either noise in general or a code word) which is followed by more exotic triggers touching specific things, detecting concentrations of numbers(I.E. if a certain number of people stand close enough together), if the target has magic, or a specific amount of magic, the presence of a certain item. The last is extremely specific triggers for combat purposes, like if a minion is hurt to a certain threshold it, or if the intruders are in a certain condition. Other ideas I had is if a door could embedded within the inside of a door arch so that when a door is closed it is entirely concealed, activating when the door is opened, or someone walks through. Other ideas I had to place another crystal behind the first one, firing a spell if the first one is removed.
Spoiler (click to show/hide):
You mean bask in your laziness. Leave it to me, and I'll break it with some bullshit combo that you allowed every step of because the pieces didn't sound that bad.
Also, yes he's thinking of trapping the spell crystals.
Random person in the comments section of a random hentai manga- "Now I am ashamed of myself."
Me- "Posh, shame is for fools and people with friends... we need no such things, we have the internet."