|“||We should have killed Hyperion Max. We got blamed for it. Turns out they were a dick.||”|
— Baston, Ensorcelled (4.20)
Hyperion Max is a member of the Planeswalker Council who the Dragon Friends were falsely accused of killing, resulting in their arrest and pursuit by Steyr. For the majority of Season 4 the Friends are either searching for Max or dealing with this false accusation.
In truth, Hyperion Max is working with Bobby Pancakes to prevent Freezo's attempt to displace the goddess Mystra. After Freezo used a forbidden ritual to make himself immortal and to force Mystra into a mortal incarnation (as Bassbass Wihouveberry), he attempted to obtain the Lance in order to travel to Mystra's realm and take her place. Although he did obtain the Lance, Bobby intercepted him before he could pass through the portal and sent him and the other Friends back in time while erasing their memories of what had happened. Since Freezo had achieved immortality and thus could not be stopped by death nor would have any fear of mortal weapons, he could not be defeated in the normal way; Max faked his own death, and met with the friends under the alias of Ostin Powerful in order to recover a Titan's helmet with planar travel powers, then entered Freezo's tower and reconfigured the portal to lead to a prison dimension beyond the Cradle, while still appearing to lead to Dweomerheart. Being beyond the Cradle, it would be impossible to leave this prison without the Lance, so Max remained trapped there (thus the need to fake his own death), counting that Freezo would attempt to reactivate the portal and bring the Lance to him; he would then steal the Lance from Freezo, use the helmet and the Lance to leave, and leave Freezo entombed without the Lance.
In fact, Freezo does use the portal, but only after the death of Bobby Pancakes; and the other Dragon Friends, Jeremy Scaleson, and Bassbass Wihouveberry come with him. Rather than abandon the plan, Max steals the Lance and leaves anyway, abandoning 4 innocent people to death by starvation in the bare planar prison. Fortunately, outside the Cradle Bassbass is able to regain her powers as the goddess Mystra and to resurrect Bobby and transport the others home, in exchange for their leave to take Freezo as her prisoner in an attempt to cure the "taint in his soul".
In A Very D&D Stream, Dave mentioned that originally Hyperion Max was going to be the incarnation of Mystra, but this was changed to Bassbass Wihouveberry later in the campaign.