Gremlins understand that they lack physical power, and thus are usually encountered in large groups that work together to defend each other and their lair. While all gremlins share certain traits in common, such as a resistance to damage from weapons save those made of cold iron, a cruel and sadistic sense of humor, the ability to use prestidigitation to enhance their mischievous plans, and their slight statures, the single trait that gremlins are most well known for is their ability to break, curse, and otherwise ruin the works of other creatures. Gremlins take great delight in ruining and breaking things, and while each gremlin race has a particular “specialty” (be it magical auras, complex machinery, coordinated tactics, or even luck itself), all gremlins are fascinated by complex devices and intricate social constructs. Nothing pleases a gremlin more than being involved in the collapse of something complex.

Although gremlins originally hailed from the mysterious realm of the fey, they have lived upon the Material Plane for countless generations. In that time, they have become natives of this realm, both in body and soul. Yet not all gremlins have managed to retain their strange powers to disrupt and destroy—the most unfortunate gremlins are not even commonly known as gremlins at all. These bizarre creatures are known as mites. While they retain the gremlin ability to use a few spell-like abilities, mites represent to their fellow gremlins the ultimate shame and horror—a fall into pathetic self-loathing and pitiful cowardice. As a result, gremlins grow particularly sadistic and violent when presented with an opportunity to torment a tribe of mites, abandoning their more subtle methods of disrupting communities and machinery in favor of all-out war, invading mite homes and lairs with tiny knives in hand and murder on their minds. Only mite tribes that have managed to ally themselves with particularly dangerous vermin generally have any chance at all to withstand an invasion of this sort, and most tribes quickly surrender to the gremlins. In some cases, the wholesale act of surrender can cool the gremlins' rage, and the attackers simply take steps to subjugate and enslave the tribe of mites, using them from that point on as a slave class to serve their whims, but in other cases not even the mite tribe's complete surrender can save them.

Against larger creatures, particularly humanoids (whom gremlins particularly love to torment and vex), gremlins adopt a much more subtle approach. Gremlins know that they lack the physical strength to withstand a fight against even the weakest humanoid societies, and thus keep to the shadows when moving through cities and villages. Gremlins seek out regions within urban areas where the “big folk” don't bother to visit often—places like sewers, dumps, graveyards, and abandoned buildings make for perfect gremlin lairs. Once a gremlin tribe establishes itself in the shadows of a humanoid society, it begins its work. Operating in pairs or even alone, the gremlins move out into the society, seeking ways to undo anything that can be undone. If a gremlin can arrange it, it prefers to leave an object, relationship, or situation in such a condition that it may seem stable and undamaged to the casual observer, but falls apart or fails spectacularly the next time it is used or encountered. A gremlin often waits in hiding nearby so it can observe the calamitous results of its mayhem, but takes pains to be well out of reach when such a disaster occurs. Gremlins know that it's not good to be in arm's reach of an angry humanoid once it realizes it's been visited by a gremlin.

In areas where gremlin activity is well established, many societies have developed unique and clever ways to both protect themselves from gremlin-related mayhem and root out the little monsters from their lairs. One common method of dealing with gremlins is to use objects known as gremlin bells. Crafted from bronze, brass, or other semiprecious metals and measuring no more than an inch tall, gremlin bells are hung from delicate chains or silken cords over door frames and windows, or affixed to precious objects. The belief is that the presence of a gremlin bell sickens the creatures and even renders their supernatural and spell-like abilities useless. Strangely enough, many gremlins believe this as well, and even when the gremlin bells aren't magic, gremlins won't risk tinkering with most objects that seem to be warded in such a manner.

Other communities take a much more active path in ridding themselves of gremlins, training small animals like cats, dogs, falcons, or even weasels to seek out and attack gremlins on sight. Tiny trained animals can pursue gremlins into their cramped warrens with ease and, when their claws are fitted with cleverly constructed cold iron spikes, can inflict significant damage on a tribe of these creatures. Many gremlin tribes have learned from such tactics, however, and utilize trained (or not) animals in their own lairs for protection.