Leeching Slug

Ammunition, uncommon
  This slug is a popular weapon amongst jungle tribes. Easy to grow, and with very poor mobility, they do not pose a great threat unless you fall head-first into an infested puddle. They can easily be used as projectiles for blowguns or slings and, with some tinkering, can be affixed to arrows and bolts. Despite the low damage the leeches inflict, their numbing saliva is very potent, slowing any creature to which it attaches.
  Leech. As a bonus action, you can attach the slug to a piece of ammunition or load it as ammunition in a blowgun or sling. On a hit, the targeted creature must succeed on a DC 15 Constitution saving throw or become ‘numbed’ as the slug sinks into the target’s skin. While ’numbed’, a creature’s movement speed is halved and it takes 1d4 necrotic damage per slug attached at the end of each of its turns. A creature can use its action to make a DC 15 Strength check, dislodging all leeches currently attached on a success. The slugs have no effect on incorporeal creatures, elementals, oozes, undead or constructs.
  Very rare variant: A numbed creature has its speed reduced to 0 and takes 2d6 damage per slug instead of 1d4.