Fate to never to die by the hand of a mortal being?
 

It's been awhile since I played the game, although had anti-magic winner ~ 2 years ago.

A sorcerer just the fate, "to never to die by the hand of a mortal being"

Does this make me unkillable by some monsters?

Thanks

Yes. Mortal beings can still sliver you for a demon to finish you off. If you ever played a summoner, its like killing uniques with summons except you are the unique. I assume the same tricks summoners use also work for monsters - poison or shard dot probably will kill you whether the caster was mortal or not.

Some monsters have the IMMORTAL tag, the rest have MORTAL; you can check in r_info.txt to see whether a particular monster is IMMORTAL or not.

Whether you are a mortal or not, poison can kill you.