The Mutant Frog
The Shiva is a frog that has eaten mutagen and grown into a massive monster able to create and destroy. The Shiva is always aided by dragonbats, make sure you don't get anywhere near it without a plan.
Shiva drops an item called "Mutagen" that can be used to craft the "Baby Ashkore Soul" and the "Gontar Soul". Shiva also drops angelic swords. It's really hard to find and battle, she can jump around and dodge your attacks. It will spawn/summon Dragonbats that will assist it.
Shiva can be found in high level (60+) Jungles very rarely.
It has a high dps and is the strongest boss MOB in block story besides Mati.