Wrath of the Lamb
is a commercial expansion for The Binding of Isaac
. It hooks into the main game and alters it permanently. The original gameplay is still present, but expanded with 100 new items, 5 new chapters, 20 new enemies, 6 new room types, 5 new music tracks, a new challenge mode with 10 challenges, and Samson as an unlockable character, and more. The add-on content is not played separately, but directly alters the original game.