A Tragic Existence (Lore)
The Demented Shark(s) were once a normal, feirce, and resilient ocean dwelling creatures, until it encountered and was infected by Coelomomyces,an aquatic fungus. As the spores develop they cause the normal shark to undergo some changes and the end result is a Demented Shark.
Taking a moment to examine the card art of the Demented Shark you will notice multiple injuries on the shark. You can observe numerous cuts/gashes, extreme scaring, and fungus-like growths from its head. What you can not see from the art is the loss of control of their body or agony of rage it feels caused by the fungus.
I suspect the Demented Shark was once a Sabre Shark based on appearance, specifically the little chin dangly bits, eyes, fins, nose, and pretty much all of it. However, this is not confirmed in either of the card’s lore.
His Potential in Battle
It seems through shear rage alone the Demented Shark is able to inspire his allies and increase their melee attack damage. This ability works exceptionally well with abilities like sneak or opportunity.
Once leveled up the Demented Shark recieves the thorns ability, to reflect just a bit of the pain they feel. This ability in conjunction with his decent health pool and 1 armor make him a viable front line monster that benefits the whole team with inspire.
When certain rulesets come around like Up close and Personal, Super Sneak, Melee Mayhem, or Equal Opportunists the Demented Shark truly shines. He is also a newer reward card with the Untame border, so he will be usable in the modern format.
Looking to the Future
Currently, there isn’t a large pool of water Splinter cards that benefit greatly from the inspire ability. There are a couple sneak monsters and 1-2 with reach, but that's it. There is also no water summoner that synergizes well, but in the near future there could be.
Chaos Legion is surely to bring more melee attackers, and likely 2 water summoners, so I believe the Demented Shark has a bright future.