Character assassins will be taught the formulas for one type of venom for each level of experience, alternating between ingestive and insinuative. However, each character is responsible for their own laboratory and material components.
The Player's Handbook rules for assassins states that there is only one level 15 assassin, but that is not true in my game; they can actually go to level 22. The assassination chart is extended to 22; the numbers reflect the difficulty of assassinating such powerful creatures.
Assassination in plain sight - at level 15 and above, assassins have a chance to assassinate a target without requiring surprise. Use the assassination table, and subtract 14 levels from success chance. This may be attempted no more than once per round, and against any given creature, no more than once per encounter (loosely defined as a day).
Hiding in plain sight - at level 15 and above, assassins have a chance to hide in plain sight. Provided that they are not being directly observed, they can effect a sort of 'unimportance' upon themselves, such that there is a 10% chance per level over 14 that they will simply not be noticed by anyone. This can be attempted no more than once per turn in a given location, and if it fails, one or more observers will immediately note the assassin acting strangely (such as standing like a statue, trying to blend in with guards, or whatever would fit the situation).
Assassination - at level 15 and above, assassins can perform standard (surprise) assassinations with their hands, feet, or virtually any object within reach hard enough to penetrate skin.