Retriever

Retrievers are very large spider constructs employed by the church of Lolth and some other powerful and/or wealthy figures in the Underdark, especially in Menzoberranzan.  They are sent after specific targets - either named individuals or by specific categories - and can hunt these with remarkable aplomb.  Unconfirmed rumors report that Retrievers are even capable of tracking their prey to other planes.  They are equipped with large beam cannons, one of which can paralyze victims.  They will paralyze the target and then forcibly plane shift them back to their master. 
These constructs were originally designed to hunt demons in The Abyss for use as slaves.