Instructions
Begin the boss fight with Death. Death will switch back and forth between a light and a dark form during the battle. The light form is vulnerable to physical attacks while the dark form is vulnerable to spells. Attack Death with Jonathan's bible weapon when it is light and attack it with Charlotte's "Temple" spell when it is in dark form.
Jump or duck to avoid the scythes that Death throws. Death will also summon chains that form a square; any thrown scythes will bounce off of this square and go in unpredictable directions. You can break the square by attacking the hands that form the square. Cast either "Dark Rift" or "Anti Air" when possible to dispel the scythes.
Attack Death based on its vulnerabilities while avoiding its attacks until it is defeated. Focus your attacks on its current form while avoiding its attacks and the battle won't be too difficult.