The Boss Wizards are a clan of players known to be reserved and always taking advantage of a situation, regardless of anyone, Terrarian or otherwise, who's also involved. They are in a rivalry with the Lost Legion.
Boss Wizards take advantage of various tactics and methods allowed by the game but that which are looked down upon by most to speed up their progression. Their provocative methods also secures their position as a very powerful guild, albeit less known, which is why no guilds have attempted to lay siege to Boss Wizard establishments, alone or with allies.
They have been known to invite players to quests and abandon them in dungeons (according to S), only to loot their bodies later. They have also been known to straight out kill players when nobody's around.
Boss Wizards often use illegal methods like power-leveling (a fancy word for mob farming), monster PK (as mentioned above), and illegal ganking, which indicates that their primary goal is not to play the game for fun, but to excel and obtain power.