Storm giants may be generated in throne rooms as early as dungeon level 13, and may appear when a throne at this depth or lower is looted. Storm giants can also be generated if a chaotic spellcaster casts the summon nasties monster spell. They are also eligible to appear in the Valkyrie quest and Caveman quest, which have H giant humanoid as the second quest class, though in practice this will usually not occur by the time the Quest is actually finished.
Storm giants are usually not seen until late in the dungeon, but are generally not that much different from other giants. They have a fairly strong weapon attack with the same hit dice as fire giants, and can move at the same speed as an unhasted hero - but most players should have sufficient experience with their kin (and usually a source of speed) by the time they encounter storm giants. As with most giants, be wary of any attack wands they may spawn with - taking advantage of their low monster magic resistance is generally a good idea.
Giants have always walked the earth, though they are rare in
these times. They range in size from little over nine feet
to a towering twenty feet or more. The larger ones use huge
boulders as weapons, hurling them over large distances. All
types of giants share a love for men - roasted, boiled, or
fried. Their table manners are legendary.