Well crafted arrows with grey fletching. Nock is enscribed with a stylized snail-shell.
Being struck by this arrow slows down the target. Affect per arrow is a -5% decrease in movement-based defences. If the target is brought to -20% net penalty*, they become immobilized. The effect of each arrow ends after 1 minute.
The arrows inflict significantly less damage then normal arrow types, typically half of that of normal arrows.
The arrows were created by Imperial fletchers to help their half-blind emperor with his hunts. His retinue would use these arrows upon hunted creatures to allow their liege to have a chance to hit them.
The arrows also impede their own use, being difficult to extract from the quiver, even if the quiver is nearly empty. As such, rapid firing of these arrows is not possible unless careful preparation is made.
Inspired(stolen) from Team Fortress 2's Natasha. This is probably the shortest sub I've submitted.
*Any bonuses are lost first, so a target with a bonus of 20% would need to be hit by a total of 8 such arrows before being immobilized. D20 based systems would mean a -1 Dex modifier per arrow, with immobilization at -4.