Originally Posted by Myrdin

This event doesnt even drop Life Crystals at a set rater, rather than as RnG chance

I pretty consistently get 6 Life Crystals from completing ?-8, they drop either from the last chest or the pests right above the last boss, not sure which of those two, but I suspect it's from the pests. However, in the reward screen, they have a tendency to show on a line below the other boxes, it almost drops below the screen. So for Life Crystal farming, make sure you get those pests above the final boss as well.