Gunther isnt a normal dog hes a kalb jinn

(Dog demon) the information on this species is in the image below

Gunthers purpose as a kalb jinn is to manipulate and make others the worst most evil versions of themselves hence with Trent, Kalb jinns are a sort of parasitic species as there really isnt a way to get rid of one, they always come back into your life disguised as friends and convince, manipulate, groom and brainwash you into doing purely evil things

You can sell your morality to one for many things including money, happiness and power

Reaper wanted power, he sold whatever was left of his morality to Gunther and in return Gunther gave him forms that he could transform into

Form number one, Avcı 

Avcı is a bigger, stronger and more powerful version of Reaper

Reaper often transforms into Avcı when he feels powerless and needs to feel bigger

Avcı has a cold, grumpy personality unlike Reapers cocky personality

Avcı can also be triggered by sadness

Avcı co own polorus with Gunther

Krypton

Towards the end of the lore Avcı seperates from Reaper into its own being due to being strong enough to separate

this being is known as Krypton and is basically the same as Avcı just has his own soul and solo body

Fez

Fez is the combination of the souls of Avcı AND Reaper

Reaper usually transformed into him when he felt overstimulated or angry

Fez eventually gained his own consciousness and became emotionally powerful enough to seperate from Reapers soul and he became a doberman

(this is because not only is Reaper half doberman but Fez also exists because of Gunther and Gunther is a doberman)

His main goal is to work with Reaper to overthrow society as we know it and basically rule the world But they eventually have a few disagreements and Fez gets greedy and wants everything for himself and ends up ditching Reaper to do things the way he wants it.Their main disagreement is that Reaper is too soft on their captors and Fez wants harsher punishments and also ethnic cleansing to purify the eurasian race which Reaper disagrees with as he still wants other races.Fez ends up negotiating with khan. Fez ends up working with Khan (khan doesnt know Fez is against Reaper) and Khan funds a lot of Fez’s stuff. Basically Fez co owns Turkey now and slowly overthrows Khan and then he becomes dictator. Khan then co owns poland with Reaper (mainly the occupied ukrainian bit) and works with him to overthrow fez and that starts a war basically

Fez starts to take a liking to Otys the mayor of Istanbul and makes him his assistant and hitman and he takes out anyone against him, he also frequently makes Otys wear a gimp suit (**but this is only canon in their non feral forms because im not drawing a literal animal in a fucking fetish suit and neither should you**)
They both plan to take over the world basically. He also works with Marcus Napalm the mayor of London as Marcus shares the same interest in overthrowing the elites as Fez and also shares similar agendas but they are often fighting because Marcus sees Fez as crazy and irresponsible and Marcus is more calm and 'normal' but Marcus is also a megalomaniac just like Fez.

Fez's independent form and Otys (the Labrador in the muzzle)

Marcus Napalm

Marcus ends up killing the Prime minister, Phill Gorming of the UK and getting elected after running for prime minister with his canist party without the general public knowing he did that

Low quality art of phill that i made in like 2 minutes

Fez and Reaper