[X] Interact with the obelisk - Examine it more closely. Look for any significant symbols or markings.
[X] Talk to Lucas and Sierra and tell them that you are pretty sure that your magic is safe to use once you have figured out a spell and you would really like to create some more light so you can study the obelisk properly. Try your best to persuade them.
-[X] If they are okay with it, cast Light.