13 guaranteed samples can be found, in the following locations (magenta crosses on map):
- 6 samples are in Xaselm, 4 in the Experiment Chambers zone and 2 in the Sanctum of Vivisection zone
- 3 samples are in Bruscus Dannus' House in Highcross
- 3 samples are in Mirili Ulven's House in Highcross
- 1 sample is in the House of Dementia
Void Essences are obtained from nearly all varieties of Flesh Atronachs. Even summoned Flesh Atronachs have Void Essences. The only exceptions are two specific "Flesh Atronachs" found in Xaselm as part of the Rebuilding the Gatekeeper quest. Also, some already-dead "Failed Experiments" may be similar in appearance to Flesh Atronachs, but they do not have any Essences.
In most places where Flesh Atronachs appear, they are possible at any level. At levels 9 and higher, Flesh Atronachs can also possibly appear in place of Zealots.
Places with guaranteed respawning Flesh Atronachs at all levels include (red circles):
- Gardens of Flesh and Bone has 3 guaranteed (4 more likely).
- Xaselm has 1 guaranteed (4 more likely).
- Ebrocca is likely to have 2 Flesh Atronachs at all levels.