Guys help, so I am trying to drop Brakk. I did invasions against Grineer, got the message inbox. I was told to jut run Lex on Ceres and they would spawn, but they do not. Is there anything else to do for them to spawn? Help please!
There's a % chance that the G3 will appear in the first few minutes of any Grineer mission. So, just do a bunch of short-ish missions and they'll appear eventually. IMO it's not really worth actively trying to get them to show up.
Yep, I believe it's literally any always/normally Grineer node they can spawn in. The chance is just low and some missions are better for getting it to happen.