Markaat is some strong evil entity who has all evil powers in him that's why he is referred as mrityu ka Devta as he helped cheel clan to gain human form & cheel clan r highly scared of him entering in their lives as they will loose d control & markaat will rule over them.
I feel markaat don't have any physical appearance or I say maybe he was once alive but as death is universal truth so he also died but his evil soul remain dint faded away , if he was alive then I don't think cheel clan would had placed a stone statue of markaat.
Chandrakala also said no one knows where is markaat, ye dekhna zaruri fake markaat ne markaat ki place kaise li . Ballu & cheel clan reads excluding veer know about shatruji reality that's why ballu was again & again warning bani . In kalyug cheel clan hardly visit markaat except Shukla .
Teer's grave is present in markaat cave when bani was acting to drag teer's coffin to instigate veer to attack her , veer asked her not to open d coffin as teer will not able to tolerate moonlight.
I feel Chandrakala herself will bring real markaat in singhaniya family as I have doubt cheel clan will ever approach markaat. To come in real world markaat definitely need a human body , so I feel markaat soul will enter teer's body & make entry in singhaniya mansion.
Teer don't have any important role but still that second moon never disappeared when naag guru wonder how can be two akesh possible ? So I feel teer will turn as markaat & returned to life.
Sharad will definitely nail in negative role 2. Veer has to fight markaat to save his clan & bani from markaat thou he is emotional towards teer.
Finally defeating markaat veer will end d darkness spread in his clan & lead his cheel clan to right direction as cheelraj.
Teer background song " nayak nhi khalnayak hu mein " my theory is inspired by this song😆
This song is made from a villain's pov but this song lyrics has a lot of meaning.
"Sabko pata tha main kamjor hu mein isliye aaj kuch aur hu ".
I guess this line suits teer as he was kept aloof from d family thinking he is mentally unstable , so he returned in different form.