6How to craft it
Mythril Anvilhow the bouncing works
Fire one into a wall and it looks for something to hit. If an enemy is in line of sight at a reasonable distance the dart snaps toward it and keeps its speed. With nothing valid nearby it behaves like a normal dart, punching through bodies or ricocheting off tiles as it would anyway. Every redirect shaves damage off, so the last hit of a long chain is much weaker than the first.
where they earn their cost
Tight spaces. In a corridor or a small arena the dart keeps finding walls and keeps getting sent back at something, so a single shot lands several times. Fired across open sky it just flies straight and you paid for a feature you never used.
The other case is anything with more than one body to aim at. Multipart bosses, a boss that spawns a swarm, and long segmented worms all give the dart a fresh target on every bounce. Global invincibility frames apply on hit, which caps how fast you can stack damage into one small enemy, so the gain is real specifically when there are several things to spread the hits across.
handling
Gravity does not affect them the way it does other darts, so the aim is flat and predictable. They also glow brightly in flight, which makes them easy to follow in a dark cave and easy to see where a shot went wrong.