He claims the souls of those who died and takes them to the afterlife. It is useless to fight him as he can't be destroyed for there is always death, there is only life because of death. The Angel of Death cannot be stopped and never gives up a claim. The only way to change the fate of one destined to die is to make a plea to the Angel of Destiny.
To Summon the Angel of Death
Through day and night,
Create a breach;
Past dark and light,
Extend our reach.
Though we've not felt our final breath
Let come at once the Angel of Death.