Assuming you have a Character Movement component on your character, you can change the gravity by calling the “Set Gravity Direction” node. The blueprint below gets a reference to an actor with a tag, and sets the gravity to the direction from the character to the actor found, normalizes it, then scales it. I hope this helps!
Oh and depending on how you’ve got the movement set up, you may have to alter some logic for when the character goes “upside down”, at least from the screens perspective.