The stone giant, H, is the weakest form of giant. It is virtually identical to the essentially non-existent giant monster (which normally appears only as corpses) except that it is possible for stone giants to be randomly generated. As with all giants, they have a chance of being randomly generated with a boulder and some gems in inventory.
All was well, until one day they met a thunderstorm—more than a thunderstorm, a thunder-battle. You know how terrific a really big thunderstorm can be down in the land and in a river-valley; especially at times when two great thunderstorms meet and clash. More terrible still are thunder and lightning in the mountains at night, when storms come up from East and West and make war. The lightning splinters on the peaks, and rocks shiver, and great crashes split the air and go rolling in tumbling into every cave and hollow; and darkness is filled with overwhelming noise and sudden light. Bilbo had never seen or imagined anything of the kind. … When he peeped out in the lightning-flashes, he saw that across the valley the stone-giants were out, and were hurling rocks at one another for a game, and catching them, and tossing them down into the darkness where they smashed among the trees far below, or splintered into little bits with a bang. Then came a wind and a rain…. Soon they were getting drenched and their ponies were standing with their heads down and their tails between their legs, and some of them were whinnying with fright. they could hear the giants guffawing and shouting all over the mountainsides."