As far as I know, there are two missions which can only begun if you encounter one of two ultra-rare NPCs. One of them is Hastened Dispatch, initiated by fighting Caelon, Dark Dispatcher
http://galaxylegion.com/wiki/index.php/ ... Dispatcher.

What is the other one, and are there any others. Can the Wiki please be updated to properly list that NPC like Caelon is marked in the Dark Smuggler's listing?

they're not ultra-rare... they're "Extremely Rare"

Caelon... make sure you have at least 2000 scan when looking for him
Silthion Hybrid Larva... make sure you already have Controlling the Silthion as an active repeatable quest and have 1500 scan when looking for it

*hands you a wiki pen* feel free to make edits whenever you find something inaccurate or incomplete

They may be technically Extremely Rare, but in the month plus Caelon has been active, I've gotten every other extremely rare, some of them more than once, in the game that I'm eligible to see, and my scan is over 4000. And I'm level 490.

as for editing the wiki, I can't find the edit page link. Maybe I'm just missing it. Silthion isn't listed on most of the pages that list "Other Factions" and in fact on the Hybrid Larva page Dark Smuggler isn't listed as an "Other Faction"
http://galaxylegion.com/wiki/index.php/ ... brid_Larva

i did not kno u needed to have "Controlling the Silthion" as an active repeatable ? well ty LY i was about to do a massive NPC run with the aim of getting both unlockable missions in one shoot i guess il have to postpone it for a while more Ehhhh i guess this just gives more time to gather nrg cubes and tries

first make sure you're logged in on the wiki... if you're not logged in you won't see the edit button
second, the edit button is under the X in Galaxy