one of the major revelations and questions of TES III: Morrowind is whether ALMSIVI ( the tribunal of living gods who govern the land of morrowind during from the first era , to the third era in which the game takes place ) , have killed saint nerevar or not. nerevar was the leader of the chimer , the elves who would later become the dunmer / dark elves. almalexia , sotha sil and vivec were all friends and advisors to him , and in the case of almalexia and vivec even wife and lover. during the battle of the red mountain , during which the nord , dwemer and dunmer battled , nerevar was made aware of a plot by the dwemer that could spell doom for all of tamriel. i will not go into the specifics here , as the post would get too long ( it's about the numidium , the brass god the dwemer tried to build. very cool!!! also the reason the dwemer completely vanished!!! ).
the plot involved the very heart of lorkhan , hidden within the fiery depths of the red mountain , one of the immortal spirits / gods which predates the creation of the physical world , and whose insanity birthed it. accounts differ on what happened exactly , and as it stands all of them might be true simultaneously. though , contradicting the official version of events as told by the tribunal , almalexia , sotha sil and vivec killed nerevar in the heart chamber of the red mountain , and used the heart of lorkhan to gain immortality and godhood.
which brings me to vivec specifically , and the insanity of their very being. the following is cobbled together from obscure tes lore and theories , which i'm sowing together for my portrayal of vivec.
now , all of reality takes place within a dream , dreamed by the godhead. the slumber of a single being. one can argue whether that only entails the mundus ( the physical world / tamriel ) , or also inculdes the aurbis ( which is the entire universe , thus also including other planes like oblivion and aetherius etc ). vivec reached godhood by partaking in the ritual revolving around the heart of lorkhan. they also reached CHIM. CHIM is a state of being in which one recognizes the entirety of the universe in it's untouched state ( before the mingling of anu and padomay which created the physical world ... it's complicated lmao ) , and is able to manipulate reality as they please , so long as they remain within view of the Tower ( which is the true shape of the universe , and only glimpsing and understanding it may grant one CHIM ). if one fails at CHIM , they zero-sum , which means they will be entirely erased from all of existence. now , CHIM as a concept is kind of selfish in nature , because it is a path to enlightenment which firmly latches onto ones own ego.
all of this means that vivec understands all of the universe , but they still remain vivec. there is an inevitability to existence which they cannot escape , and godhood merely underlines that very debacle. there is no uncertainty for vivec , and the certainty in which they exist and form reality to satisfy their truths and lies and their ego and their lust for power is what drives them insane.
which is an interesting tragedy , for lorkhan too made use of CHIM in the creation of mundus/tamriel , but he did it wrong on purpose , creating the physical world as a prison to point out the faults he perceived in the immortal spirits. vivec knows this , and it changes nothing.