Talk:The Grustrag Three/@comment-24881581-20140429215108/@comment-24557530-20140501083941

They appear by chance. Once you got the message each non-boss Grineer-mission has a chance of them spawning. But we all know DE's RNG - so they might appear in the very next mission after getting the message or only after half a year of grinding Grineer missions or anything in between. Only hint i can give here: Run around with a full squad (4 ppl) who all got the message recently to increase the chances of them spawning.