Sword Ticks look nothing like ticks and their hazard is not limited to swords. Though, they are as small as ticks and can jump the length of a man, they are more a kind of tiny subterranean limpet, or arthropod with a very hard shell. Living in massive colonies wherever iron or it's ore is present, their great numbers and stony coloration make passages appear to shimmer.
Preferring steel above ore, they will jump onto swords, shields, and armor-- anything ferrous. Once onto the object they lock on and are protected by their shells. Strangely, they do not consume metal and, if removed, leave no trace. But it is nigh impossible to remove these pests-- even fire seems to do little-- requiring caustic chemicals or magic.
Once clumped with sword ticks metal objects become almost unusable due to the added weight and bulk. Swords become difficult to wield and impossible to sheath. Armor becomes ponderously cumbersome. Many a weapon has been discarded to a sword tick swarm.