Fire Wall is just what it says- a wall of fire. When cast, it spreads out in a line perpendicular to the point clicked on, burning all those that walk through. The width and damage of the skill increase as more skill points are invested in it.
A critical note:Since a patching some time ago (source please), this skill has received a cool-down time to prevent clever players from spamming a whole room full of them. While this may or may not be bad news to you, the good news is that it also has increased damage now.
Lore[]
This skill, which allows the Sorceress to raise a barrier of flame to block her flanks from attack, gives her and her allies a tactical advantage. Any creatures unwitting enough to attempt to cross the barrier will feel the full force of these flames as they advance to their ruin.[1]
References[]
↑Diablo II Manual, page 86. Blizzard Entertainment, 2000.