The Thanatos Haven Lich Ra'Zan.
He was the Quintessential Thanatos Embodiment of the Absolute Dynamis of Extremity that held 21 Boundaries within it!
He could exist from the moment the Dynamis was Recorded as now that he was out, even death could never truly reclaim him unless the Thanatos Perennial Yggdrasil of Extremity was destroyed.
'Death.'
BZZT!
The bright verdant flames in his sockets blazed as this concept that was at his very core buzzed with wonder!
With it ringing in his deathly will, he gazed at the battlefield before him as what he saw was very different from what others saw.
His vision showed the myriad of beings represented as brilliant illusory hearts of differing sizes and intensity!
These hearts were filled with life, concepts, and everything that defined these beings.
The Avernus Clan Elders had their vast majority of forces showing illusory hearts half the size of the Haven Lich himself.