Bahhhhh. human Assassins are 2nd rate. The most fearsome assassins are ashraks.
Ashraks are very few and far in between. It takes many hundreds of years to hone an ashrak. Ashrak are highly skilled warriors that are able to survive for long periods of time in enemy territory.
They feel no pain, they can go for several days without food or water. They have invisibility technology. They will finish the job even if it takes hundreds of years.
They typically wear an ornate form of armor with a special helmet that covers their eyes which has a visor for them to see their environment. However, when infiltrating another society, an Ashrak discards their armor and clothing in order to appear as a member of the infiltrating culture.
The healing abilities of a Goa'uld Symbiote are fully exploited by the Ashrak who are capable of mending even the most grevious of injuries. In addition to this, they make use of specialist equipment such as the Hara'kesh which they are also capable of stashing in their mouth's which are regurgitated when needed. This allowed an Ashrak to hide their equipment making it easier for them to infiltrate a society.
Ultimately, they are killing machines.
There is only1 true ashrak that I know of, and he serves another lord.
