I'm not a good puzzle solver..

There's an offering bowl in-front of statue leading to the underdark ;/.. there are no books hinting to it cause i collect books and didn't see it. unless i missed it. can someone send a spoiler in a private message if you've figured it out? also how you figured it out please cause i want to know why i missed it.


[youtube]https://youtu.be/XNpg5VmyinI[/youtube]