Yes you do. The incantation is different for every single player, so you will need to pay attention to the gypsy woman's story and either screenshot or write down the incantation she said that Wally used. If you pick the wrong incantation from the list or take too long remembering it, then Delrith will either despawn or regenerate his health. This makes the battle take much longer. Don't be afraid to do whatever you need to do to remember it. Write it down, screenshot it, remember it by repeating it three times over. It will make the fight much easier.