Skeleton Sorcerers are fragile but powerful damage dealers. They will often be in the company of, sometimes hidden, Grasping Ghouls. Sorcerers will not hesitate to chase a player to an incredibly long distance once it chooses to attempt a Lightning Touch. Melee attackers should beware of their use of Blinding Flash.
They also have the annoying tendency to manage to perfectly time their Earthquakes so that there will be no uptime to act in between castings. Though most prevalent in hard mode, this behavior exists in normal mode as well.
When fighting them in groups, attackers will find themselves virtually always blinded. The best real counter to this is Sight Beyond Sight or Avatar of Melandru, as they prevent the condition from ever being applied.