The main features of the Wizard Patch were:
- Spells were made subject to skill level, much as weapons were.
- Different classes could gain skill with different kinds of spells.
- Spells were remembered for a limited duration, and could be cast an unlimited number of times within that period, subject to magical energy. Previously, spells worked rather like wands, being castable a limited number of times.
The Wizard Patch did not add restrictions due to shields or metal armor; those were already present starting with NetHack 3.2.0.
The Wizard Patch was entirely merged into mainline NetHack starting with NetHack 3.3.0. SLASH accepted it at an earlier date, and the name added the "EM" designation for Extended Magic, giving the modern name SLASH'EM. SLASH as such is no longer under development.
Announcement of Wizard Patch 0.7. The links in that post no longer work.
Wizard Patch version 1.0 at Ali Harlow's website, the last released version of the Wizard Patch. This is a patch against NetHack 3.2.2 and will not work with NetHack 3.3.0 or later; these already incorporate the Wizard Patch anyway.