The item is a direct upgrade to Slowing Hex. The first part is the same: you throw a projectile that slows and deals a bit of dmg. While this is happening there could be a visual effect that shows a web being woven around the character. When Slowing Hex ends the target is completely locked in place, so if a hero was in the air, he is stuck there with decreased bullet resist. The "from going untargetable" part means no using Ethereal Shift, Pockets satchel and stuff like that. The last part is applied for the duration of slow AND rooted effects, which means the only counter is stuff like debuff remover.
This item is created purely from my HATE for Etherial Shift and pocket XD
Thx again to Tryneus for creating Deadmock.