The keen stormbringer is a familiar that can only be created in the Daemonheim dungeons at level 33 Summoning. While summoned, this stormbringer has a passive ability that grants the player an invisible 4% boost to their magic defence.
The Snaring Wave Scroll enables the use of the Snaring Wave special ability for a Keen stormbringer. Using a Keen stormbringer pouch on a Summoning obelisk creates ten Keen stormbringer scrolls. The special move deals a more damaging attack that is 50% more accurate, deals more damage, and immobilises the opponent.
This article on a Summoning familiar has an associated dialogue page. Click here for a transcript of possible conversations with this familiar.