I like the Bionicle 2015 sets, I have all 6 toa and the Earth protector. The main problem for me is the lack of villains and Lord of Spider Gimmicks for me is a bad set. Im thinking of Invasion of Below sets to repurpose to fit the Bionicle story as HF makes some fine villains if I do say so myself. So far I have Tunneler Beast( It looks like a skull spider with a head and claws) as a enemy of the Fire Protector/Earth Protector that lays Green Skull Spiders. Its name sticking to the cheesy use of skull, shall be Skull Bearer and lives in the Fire region/Earth region. Im working on a cool display to show you fellow Bionicle/Lego Enthusiasts. You guys have any other Ideas on HF characters we can repurpose for Bionicle, tell me below! and have a good day.
Well, if you have any bionicle pieces, why don’t you make some villains, instead of using monsters from hero factory?
Maybe Xplode or Corrodor. They look pretty ‘skullish’ to me.
ding ding
You can use all of them since its the same build system. What CCBS sets do you have prior to Bionicle?
What exactly is the point of doing this?
Any villain from Wild Planet or even Brain Attack would fit into the setting of Okoto as pseudo-Rahi
I don’t know most of the Brain attack villains don’t even look like animals their just humanoids with animal heads.
I’d say the Invasion from Below Monsters, since they all have trans pieces like the new BIONICLE sets.
I suppose you’re right, they wouldn’t work as wildlife, but potentially servants of Makuta in future waves.
As @btmdreadnought said, the Savage Planet animals would make good Rahi. Though like everybody else is saying, why re-purpose figures when you can just make your own? The latter seems like so much more fun! 
Also, Witch Doctor has a ton of red ball joints. Really useful. plus two skulls for Skull villains!