Velroc
Image by James Zhang, © Wizards of the Coast. Accessed at the Dragon Magic Art Gallery here
[I guess Dragon Magic had to prove the latter part of its title by having both an anti-magic dragon (the spelleater) and a wild magic dragon (this guy). My version differs somewhat mechanically from the original, but it meets the same design goals--it can redirect and duplicate spells cast near it. I also changed their alignments from CN to CE, based on their listed ecology and behavior.]
Velroc CR 12 CE Large Dragon This creature is a blue-scaled, bipedal dragon, with a beaked maw and a crest of feathers. The light plays off of its scales in an odd way.
Velrocs are wyvern-like dragons infused with wild magic. Although they are more intelligent than their wyvern progenitors, they are even crueler, viewing all non-dragons as prey to be tormented before being killed and eaten. Velrocs prefer to lair in rough terrain, swooping down over the plains and flying for great distances in search of fun-looking prey. They often target well armed and defended groups intentionally, looking to test their mettle, rather than resort to eating mere animals.
A velroc’s abilities come into play most when fighting spellcasters. They can mimic spells they see, although this copying must be done quickly or the velroc’s disordered mind rapidly loses track of the spell. Their sting is no longer venomous, but instead carries a curse that weakens the magical ability of those afflicted. And they can redirect spells cast near them, causing mages to injure their own allies or affect the velroc with beneficial spells by mistake. After a few rounds of delighting in the chaos these magical feats cause, a velroc will typically lift a light-looking adversary in its claws and fly away with them, dropping them from a height if they struggle too violently. Velrocs value their own safety highly, and will usually flee if outmatched.
Velrocs are solitary creatures, simply because they distrust and hate members of their own species as much as they hate other species. When velrocs come together to mate, they typically fight over which parent will get to raise the children and indoctrinate them with their various values, and these fights are often fatal to the weaker parent. Young velrocs are treated as little more than slaves by their surviving parent, until they grow large enough to possibly challenge their parent for dominance, at which point they are driven away, fled from or killed. Velrocs are highly territorial, and battle other creatures for control of their hunting grounds—the exception are true dragons, which velrocs fear.