Traducerea - Engleză-Turcă - Ares was dead..And though Olympus beckoned,...

Ve yine de Olympus eliyle işaret etti, onun ölü bedeninin görünüşü hala aklından çıkmıyordu...>
ve Olympus buna rağmen, onun ölü beden görüntüsünün hala aklında çıkmadığını (eliyle)işaret etti,

his mortal existence = what he did when he was alive (I think)

This is a really hard one to translate, because it's not clear who "his" and "him" refer to. Here's the original, as I found it on a website (from a war game) - each one of these is a caption under a different picture:

Kratos, the Ghost of Sparta, had taken his place amongst the Olympians as the God of War.

The bloodshed, the relentless battles had finally brought him here.

Ares was dead. And though Olympus beckoned, visions of his mortal existence still haunted him.

Kratos knew that this was not a mere vision. For with the gods, nothing was ever as it seemed.

The vision of his past set Kratos in search of answers. Answers that lay in the temple of Poseidon, deep within the city of Atlantis.

Olympus is the home of the gods, by the way. I think that Olympus has invited Kratos to join the gods, but he (Kratos) is still haunted by visions of what he (Kratos) did when he was mortal (alive) - bloodshed.

Ares ölmüştü. Ve yine de Olimpos çağırdıysa, yaşamda yaptıklarının görünüşü hala aklından çıkmıyordu.

Ares ölmüştü ve Olimpos (onu) çağırdıysa da, yaşarkenki hayalleri hala aklından çıkmıyordu.

It's not "yaşarkenki hayalleri" it's "yaşarken yaptıklarının hayalleri" if that works. Actually, that's not right either, because he's not dead - he's just becoming a god, so it's when he was mortal, which means an ordinary person (not a god).

Yapılmış olanın hayali olur mu ? Ancak "hatıraları" olur. Hayal geleceğe ait beklentilerdir.

Yes - that's right.

Thank you both for your help Kafetzou and Merdogan !

I think we can translate "mortal" as "ölümlü".
So the final translation would be:

"Ares ölmüştü ve Olimpos onu çağırdıysa da, bir ölümlü iken başından geçen anılar hala aklından çıkmıyordu."

Do you think it's ok ?

I'm not sure. The memories were not going through his head when he was mortal; they were the memories of what he had done when he was mortal. Is this clear in the Turkish version?

It is for me O.k.

I think it's clear.

I'm validating then, thanks again.