Before entering the Deathbed Dream, ensure your attributes are optimized for Elden Ring Runes the fight:

    Vigor: Fortissax's powerful AoE attacks can one-shot lower-health builds, so invest in Vigor to increase your survivability.

    Strength/Dexterity: Depending on your weapon, allocate points here to enhance your damage output.

    Faith/Intelligence: If you're using incantations or sorceries, boost these attributes to improve spell effectiveness.

Additionally, spend any extra Elden Ring Runes on upgrades for your weapons and Spirit Ashes. A +10 weapon or fully-upgraded summon can make a significant difference in Elden Ring Items this battle.