How to get specific type orc?

[Orome]

I am looking for Mystic tribe assassin, does anyone know how to find one?

[Deo]

It's random.

The main source of orcs for me was Fighting Pits.
From Maggots to Warriors to Champions - those can provide great orcs. Dig through all pit fights of 4 captured regions, it's pretty fast.
If there will be no needed orcs, just kill those with your specialized pit fighter ologs.
Available orcs will be low level though, so maybe not what you are looking for.

Then comes Vendetta missions.
Usually in vendetta fort there will be both target and some captains. Some of them can be Mystic Assassin. It's the fastest source of high level (your level) orcs to upgrade some legendary gear sets.

Main issue of Vendetta orcs is that online Vendetta can contain bugged/hacked orcs with wrong letters in their names, which will brick your save - if you put them into your Garrison.

[Orome]

Currently I am looking through sieges, both defence and offence. I found one in pit fights but all orcs in my regions are above level 75, so he died pretty fast even though I did put an orc with massive disadvantage against him. the only way I can think of getting an orc from pit fights is shaming one of mine enough to make it lose.

Oh well, it's really unfortunate that I have to find one at random. :/

[Deo]

Originally posted by Orome:

the only way I can think of getting an orc from pit fights is shaming one of mine enough to make it lose

Well that's how you do it. Worse than Death can make orc from lvl 80 to 71 in just one shame, so it will be quite fast.

In this game a lot of stuff is random, and it feels good and rewarding, when something actually clicks in orc.