You have to do four separate things, and cast at least 3 spells (maybe more to get the burning light stacks quickly) to get the set to proc:
1) cast a spell that generates stacks of burning light, and accumulate 4 stacks of burning light ( a passive achieved by doing damage with aedric spear abilities)., then burning light does damage: this is the first condition
2) cast spells that generates a second stack of 4 burning lights , that then does damage
At the very best, it takes 2 seconds for each of those steps, but it could take as much as ten seconds in combat!
3) find the circle somewhere on the ground-- it only lasts 6 seconds, so find it fast!
4) Cast an aedric damage spell to do some damage-- THEN the set will proc a (SMALL) damage proc!
Really, this is just terrible design. Compare this to tarnished nightmare , where it procs automatically every 8 seconds when you crit. And, it does MORE damage than this set!
ZOS, before you introduce new sets, you should make sure they are at least as good as the top ten existing sets.
I know there arent many new ideas out there.