Oh my god if it is I’m going to fuckn cry
Of course not, he was cremated and had absolutely no reason to serve the twins over his master Soma.
Well, they never saw him ACTUALLY being cremated, the corpse could have been hidden by Undertaken and secretly revived with the purpose of serving another master, simply highlighting his role of butler with no care for who the actual master is. After all he was quite the powerful character, having him protecting the new "Ciel" could be an advantage (and at this point, it wouldn't even be so strange if Agni's killer was actually Undertaker, even Sebastian mentioned that the killer must have been some sort of supernatural being).
Sorry for the long flow of thoughts.
Ir doesn't make any sense, would be easier to capture Soma and blackmail Agni for that than just killing him like that (when the target was the prince). Agni is sadly dead.
There can be a new character, like a comment said "there can be more than 3 butlers". And Polaris looks nothing like him.
Mm if Undertaker killed and then revived him in the "zombie" style, then Undertaker could have planted whatever idea he wanted inside "Polaris"' head. For example, he could see "Ciel" as Soma, hence feeling the need to protect him and work for him.
Though, we're in the speculation zone, so why not guessing? ╮(￣▽￣)╭
Don't be stupid, it's not agni. Polaris was the one that killed agni and Agni wasn't a past Phantomhive servant.
Could Polaris be Agni??? D:
No pls no