Shardblades are the main magical weapon in "The Stormlight Archive." Each blade is bonded to its owner, who summons it into existence and dismisses it again when they're done. The rest of the time they have no physical presence. A shardblade can cut effortlessly through pretty much any inanimate matter, except for a kind of power-infused armor called Shardplate. When they strike living flesh, however, they kill it without cutting it. Most of the Shardblades known at the start of the story are improbably large and ornate; fortunately they are also extremely light. There's a LOT more to Shardblades, but a) it's complicated and b) spoilers.