Assassins are masters of a fast and silent attack. They often appear as agents, informators, hireable bounty hunters and instruments of personal revenge. Their skills in anatomy, stealth, poisons, dark arts and street smarts allows them to execute their tasks with a shocking preciseness...
Most of those thieves who choose this kind of "profession", are examples of the "traditional" style of assassin, who hide in the shadows with their deathbringing blade. Warriors and fallen knights hide and exploit the advantages of the surprise attack. Magicians can be the most fearsome assassins of all, because they use their magic to be invisible, and strike so swift that there is zero chance of failure.
Being an Assassin grants all Thief skills - Basic Tracking, Basic Smuggling, Basic Forgery, Basic Stealth - but also grant additionally Advanced Stealth, Advanced Swordsmanship, Advanced Archery and the ability to wear Light Armour.
In the video game adaptations of the FRPG, Assassins are a compromise between Warriors and Thieves. They can use the majority of weapons, but are severely restricted in terms of armour. They have more hitpoints than Thieves, but less than Warriors. Just like Thieves, they are offense-oriented, meaning that they sacrifice defense for offense and speed.