Going off the work byTrainer772 Here I've been working on completing my Codex.  Of course, that topic was only updated through 11.5 and there have been many changes since then and some things that had little or no information.  So I'm going to share what I've found so far in my attempts to complete my Codex and what "research" I've done into some of the more rare entries.  Also, I'm on the PS4 so I don't have access to the Update 13 Codex yet and nobody has updated the Wiki so I'm not sure what is added.

General Tips:

  • Loki may be great for stealth but Nekros has Shadows of the Dead.  Stealth scans count as 2 scans but if you scan then kill them then Shadows of the Dead you can scan them again which is useful for a lot of these rarer enemies or when stealth fails (almost always).
  • Rare = Alert.  Rare enemies tend to spawn more often (if not only) in Alert missions.  If you want to hunt down those elusive Nauseous and Toxic crawlers be prepared to solo alerts by yourself.
  • Scans are not lost if the mission fails or in anyway fails to complete.  Very useful for Alert missions.
  • Alerts can be completed for the reward and then played again.  If you complete a defense Alert on Egeria, Ceres for example scanning all the Powerfists and Flameblades you can you probably didn't finish all the scans if you were playing with a team.  Assuming you don't want to fail the Alert a bunch of times to finish the scans you can manually select Egeria, Ceres (for this example) and you'll probably end up joining the Alert mission (in this case it's normally an Exterminate mission I think) with the chance to scan more Powerfists and Flameblades.

Research - Please keep in mind this is all personal expereince and until recently I did not keep exact records of level.

Nauseous Crawler

  • 15-18 Infested Alert (Sedna)
  • 15-18 Infested Alert (Sedna)
  • 15-18 Infested Alert (Sedna)
  • 15-18 Infested Alert (Sedna)
  • NONE:  20-23 Infested Alert
  • NONE:  20-24 Phorid (Phobos)

Toxic Crawler

  • 12-15 Infested Alert on Mars
  • 14-19 Phorid (Jupiter) (1 per mission MAX)
  • NONE:  20-23 Infested Alert
  • NONE:  20-24 Phorid (Phobos)
  • Eris

Lobber Crawler

  • Wave 15/20 in ODD
  • 14-19 Phorid (Jupiter)
  • NONE:  20-24 Phorid (Phobos)


  • Alert on Ceres


  • Alert on Ceres

Leech Osprey

  • Cyrpess, Pluto

Scavenger Drone

  • Themisto, Jupiter - still working on this one

Anti MOA

  • Elara, Jupiter


  •  Derelict Survival - I will be confirming this one

Frontier Regulator (Same name, two versions)

  • Oro, Earth (Also useful for hunting down those damn plants)
  • Hall, Phobos (1-2 should spawn per terminal along with some randomly spread out)


  • Oro, Earth
  • Look near any bodies of water and also near the Toxin Injector.
  • If manage to remain undetected while scanning these can be stealth scanned for 2 scans.

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