Personally the knight inspired Tahu designs are my favourite :3
Although the villain shares elements with the skull villains, his design features attributes that were given to the 'demonic' beings in the concept art - which appeared to have been where the summer 2017 storyline was taking place as we see the Toa in a shadowy realm.
The villain itself includes pieces released recently in Star Wars 2016 summer sets, a waist swivvel from the 2016 Winter Wave and transparent bones which were going to be introduced as a feature for the 2017 villains.
The setting is also similar to the very last piece of concept art teasing the Toa entering the shadow/demonic realm to confront Makuta. He likely was not going to die and they just wanted to create impressive concept art, but i think its definitely something worthy of a bit of discussion as to whether Lego actually would have killed off Pohatu or another Toa.