My experience with these organs is that farming the tough ones in the palace is a waste of time, I am about 1/200 for them over the course of several months. I took 4 hours in the garden to get 5 of these organs, i've even come back to help others and it took significantly less time. Hope it helps, i did it solo, it's also alot easier to solo in the garden using the terrain to your advantage.
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