In Mass Effect, Where can I purchase Biotic Amp Interface X category and Omni Tool X category? Or can I only find it on missions?
The quality of items that you find, either from containers or from merchants, is based on Shepard's current level. Here is a base chart detailing which quality of items will drop at which level:
Rank I II III IV V VI VII VIII IX X Level 1-6 7-12 13-18 19-24 25-30 31-36 37-42 43-48 49-54 55-60
For standard containers, that is, containers that have no encryption, along with normal enemies, the above chart is followed. For containers that are locked with hard encryption, or for "special" enemies, a modifier of +1 may be added to your current level, and merchants may add a modifier of +2-4 to your level. Note: these modifier values are "for examples" and vary depending on the enemy, the container, and the merchant in question.
For this reason, it's often a good idea to leave Bring Down the Sky until later in the game when you have a higher level, as it will allow you to get high-powered omni-tools that are very difficult to find elsewhere.
Specifically, "X" rated items drop for characters of level 55 to 60, and are only situationally available from level 53.
I know this post is years old, but I wanted to post correct information. The Hanar merchant in the financial district sells savant. He also sells the Serrice counsel license that allows your quarter master on the Normandy to sell them.
With that being said, there's a good chance that you may not ever sew one for sale unless you use the save/reload trick. Vendor inventory changes every time you gain a level. I think the lowest level savant is VIII. After you gain a level, save before you speak to a vendor. If they don't have whay you want, reload. I stay out of talk range because it seems like it can cause their inventory not to change when you reload.
It can take MANY times for savants, colossus, and predator L/M/H to show up. I prefer the colossus, and as far as that goes, the hanar can sell any kind under normal items and alien types under non-human armors, one or both merchants in the ward markets can sell non-human, I belive the c-sect merchant only sells human (which of course can be very helpful for your main, Kaiden, and Liara since you're going to need certain weight classes), and with the Kassa Fabrications license sold by the c-sect merchant, your quarter master can sell any kind too.