There are at the moment three masks in G2 that don’t have canon powers, so lets theorize about them here! (For those who don’t know, they are the Kulta mask, Bull Skull mask, and the Beast’s mask)
I don’t have enough info to guess on the Beast’s mask, but as for the others, I believe the Kulta mask to be the mask of the undead, as Kulta can raise the dead, and the bull skull mask to be the mask of decay, as in animation, a bull’s skull is what you see to symbolize death or decay.
I’m not entirely sure all of these are masks to begin with. For the skellies the book seems to imply their Skull-esque masks are indeed masks, but for the beasts it seems to be a part of their faces.
On the Skull Masks, I don’t think they have powers. If they were intended to have powers I’m pretty sure at least some media would have shown or mentioned them.
Maybe we can’t theorize on those Masks, but what about the following?
I thought think that would be OK to speculate and theorize on ideas on these since they are part of G2.
Okay-Groovy?
EDIT:
I suppose we could technically remove the GMoSS, but it never shows up in the story. Just the comics.
Well in the animations its hard to see but Kulta isn’t wearing his mask when he puts on the mask of creation.
I think they are more or less the equivalent of what the Kanohi were to the Matoran. Like, they don’t have powers but they give the user life/strength. Because in RoSS Kulta and Basher lose power after their Masks are taken by Ekimu. I assume he did that to ensure they didn’t use their strength (especially Basher), to break out of prison.
I don’t think the Skull Masks do anything except what I’ve said above.
Allows the user to stop Bionicle exclusives from ever leaving Russia 
I think the exclusive Masks have no story relevance at all.
exclusive masks: not cannon from what i can tell
skull and bull skull masks: basically the matoran kanohi, they just give the user enough strength to carry out whatever they need to do
Villager masks: same as skull bull and skull masks. no powers but if they arent wearing them, nighty night sleep tight dont let the bed bugs biite
protector masks: limited elemental control ( as shown when Narmoto created a small firework from his hand) and enhanced movement and strength (like captain america). i also theorise that they may charge the protectors elemental blasters.
original toa masks: honestly at this point i think that they are just basic, powerless masks the same as villager masks. we havent seen any toa use elemental powers with them on (we have seen toa such as pohatu use their weapons to mimic controlling their element) but people keep saying that they have some elemental control so meh, doesn’t mind me
golden element masks: near full elemental control (goes without saying) also, it seems they are connected to ekimus subconscious at the same time (likely a power he crafted into them purposely)
unity masks: same powers as the golden masks (as shown in journey to one, the toa can control the elements still with these masks such as lewa moving the trees and kopaka creating ice slopes) except for the mind connection to ekimu (presumably) and are instead connected mentally to the respective creature.
golden unity masks: same powers as the unity masks except they allow the user to unify fully with a creature, gaining powers from them (rather than just accessing memories like umarak does)
mask of creation: allows the user to change the form of matter ( think transformium from transformers 4) eg. water changed to limestone bricks
mask of control: mind control ( pretty self explanatory)
mask of ultimate power: all six elements
Is this from the books/comics?
I think the skull masks are funeral masks because if you think about:
Ekimu was buried with his own special funeral mask so we can assume this is a tradition in Okoto
The skull warriors (who all wear skull masks) were reanimated corpses OF Okotans.
They probably aren’t their skulls as we see Kulta take his off.
Just my theory
No idea about the Bull Skull Mask though
Oh yeah.
Forgot about that…
although there is no evidence to support this i think that bull skull masks and skull masks are literally the ripped off fronts of skulls from dead okotans and animals that the skull creatures use as masks ( sort of a tribal thing )
Maybe the Bull Skull Masks and the Skull Masks were forged by Makuta for the Warriors and Champions of the Arena (Slicer, Basher, and Kulta).
Except for the Skull Scorpios. Maybe they were reanimated with old Bull Skull Masks from the Arena’s past Champions on their faces…
(Until I see a fleshed-out Scorpio though, this is my thought.)
Ekimu was buried with a protector mask as he didn’t have a mask, not a skull mask.
That actually makes sense. They can’t fire continuously (episode 5) but if given time to recharge, they can fire a lot (RoSS).
@AwesomeJoel27 Ekimu was still alive. Maybe that mask kept him alive all those years?
Well he was the most honored of all the protectors so its faiir to assume that he had a special funeral mask instead of a lowly warrior funeral mask.
