How to 'proc' strange celestial?

[VladK02]

Im at the end game, last quest to finish.
Strange Celestial.

Forums say, i have to chase it down into its portal, apparently. Had I known this before...

But how to spawn it? Does it appear randomly? I have re-visited a pile of systems, including the one with the related exploraton mission that mentions the emmisarry.

But blue thing wont come back. Am I hard-locked out of this quest? It only comes once per system or key event?

[Zago Zur]

You mean the Emissary? You can have at least one encounter with it in the early game, and it will take you to a certain interesting system. In previous playthroughs, I also encountered it in some other locations, but I'm not sure if that's still possible.

Anyway, there's a specific planet where you can interact with something to summon more Emissaries, and also set where their portal takes you. If you need help:

The star system of that planet is hidden, you won't spot it just by flying around established routes.

There is a map which shows you where the hidden system is.

The map can be found on a planet in the general region of the collapsar, something you'll visit in the late game.

Once you follow the map and find the hidden system, you can operate the Watchtower by figuring out what code to enter. At least one thread here already discusses how to do that. Different codes will make the Emissary take you to different destinations.

One particular code will let you progress with the questline that takes you to the alternative ending. It transports you to a system which you might have visited before, but there will be something new there now.

One of the other codes will take you to the system that you might have missed when you first encountered the Emissary in the early game.