Magic Quiver

The speed change is the part you feel immediately. Plain wooden and silver arrows go from lobbing in a slow arc to snapping across the screen almost flat, so you stop having to lead your shots against anything that moves. The boost even reaches arrows already in the air, which means equipping it mid fight speeds up whatever is still on screen.

A large share of the good ammo already flies at the boosted rate, so the quiver adds no speed to it whatsoever. That covers most of the special arrow types you would actually be firing in hardmode, plus the built in ammo from bows like the Phantasm, the Aerial Bane, the Ice Bow and the Marrow. The damage, the knockback and the chance to save ammo still apply to all of them. Just do not expect the flat trajectory you got used to with basic arrows.

The upgraded quivers stack only their damage with this one. Speed, knockback and ammo conservation cap out at a single copy, so wearing both burns an accessory slot for almost nothing. Once you have crafted the upgrade, this stops being gear and becomes material.