Creeping is also the act of hunting down creeps
- native nasties guarding strategic spots around maps in the 2002 hit game, Warcraft III
While hunting creeps is quite profitable, each individual creep resulting in 14-100 gold (!), there are risks associated. Creeps are powerful, if somewhat static, creatures in their own right, with a full complement of spells, auras and abilities. Each creep has a "level", showing its relative toughness, worth, and experience points given if defeated. Once defeated, creep groups or individual creeps of a certain size drop magic items that your heroes can use. Obviously, the higher level (and difficulty!) a creep, the better the item rewarded...
Creep groups tend to fall in to a few sizes - tiny groups of 1-2 level 1 creeps (eg gnoll poachers) with a "leader" of around level 3. Small groups up that to 2x level 3, with a level 5 leader - usually the first type to obtain an aura. Larger groups tend to throw together a few level 3, a couple of level 5 or 6 and a formidible boss, usually level 7, and quite deadly to the unprepared.
On top of that, the creeps usually guard the most strategic points. Gold mines are ALWAYS guarded by creeps (except for the initial one each team starts with), as are the Fountain of Life/Mana, Goblin Merchants and Mercenary Camps. Usually on each map there is also a number of creep "super groups" - guarding the lone Fountain on a map, or in out-of the way places designed to award lots of XP. These are usually in the forms of red dragons or granite golems, and usually have a few smaller siblings as well (dragon whelps and rock golems).
Creeping has come under fire from those players not used to the strategic value of this quaternary resource, saying that it unbalances the game, however creeps are totally localised, and always in the same places each game, and the same basic types appear in each strategic location as well. If seen as a "challenging resource", creeps make a new aspect to the real time strategy (RTS) that is a breath of fresh air in a genre that was threatening to become stale.