The (alternative) Obsidian Brick Wall is a type of wall which, on Old-gen console, 3DS, and tModLoader versionsVerify, largely replaces the lighter-colored naturally generated version in regard to player usage. Obsidian Bricks is used to craft the alternative version, and both player placed and naturally generated versions also drop this item.
Desktop 1.4.0.1: Removed; Obsidian Bricks can now be used to craft the natural version, and the natural version will also properly drop when destroyed (both player placed and in Ruined Houses).