A Hidden Door

"Hidden Doors can be found with Lantern or Knock."

- In-game text

 is an Obstacle appearing during Expeditions. Its Aspect is Seal.

Defeating
"There must be a door here. But without Lantern or Knock, we can't uncover it."

- When encountering the obstacle

As told in the description, Followers with or  aspects can overcome this Obstacle with a probability depending on the aspect magnitude.

Lantern
We call upon the Watchman,...
 * 1 < < 5: ... who is not Compassionate. We carry light. We might find this Hidden Door. It'll be a struggle. 30% chance of success.
 * 5 <= < 10: ... who Navigates. Our senses of sharpened. We should find this Hidden Door. 70% chance of success.
 * 10 <= : ... who Illuminates. We'll almost certainly find this Hidden Door. 90% chance of success.

Knock
We call upon the Beach-Crow,...
 * 1 < < 5: ... to whom belongs what is not possessed. We have some ability in the matter of opening. We might find this Hidden Door. It'll be a struggle. 30% chance of success.
 * 5 <= < 10: ... who opens the earth. We are skilled in uncovering hidden ways. We'll probably find this Hidden Door. 70% chance of success.
 * 10 <= : ... who sees what is lost. We bear a great power of opening. We'll almost certainly find this Hidden Door. 90% chance of success.

Success
"Faint lines in stone; a surface that yields to pressure. We've found it! The Hidden Door moves, with a grating shudder and a shower of dust."

- A Way through the Hidden Door (After success)

Finding the Hidden Door will remove the Obstacle and continue the expedition.

Failure
"Where is it? We could use more Knock, or Lantern."

- A Fruitless Search (after failure)

Failing to open the Warded Door will not put your Followers in danger but will trigger a 30s timer after which another attempt can be made.