pixel_player74486255 You don't need to open that gate, you made no mistake. All the red jars that contain prophecies are accessible without opening that.
If you've got all the 5 prophecies (marked red in maps), you need talk to priestess of thoth in town and make some milk and muffins later and give it to her in town.
Check Maps/Quest details here: https://www.diggysguide.com/egypt/hall-of-prophecy
