Their plan was simple. To get a few others who can help them against the ancient knights. The question was who can they trust. Arthur had a few people in mind, but he didn't know how to contact them in the middle of the test.
He hid the fact that he already had a crystal, the copy he got from Jonah, from Ellen as that would make her doubt his intentions. Even though he could pass anytime, Arthur still wanted to get stronger and help his friend.
Even though it looked disadvantageous for him, he was still benefiting from this. The Ancient Knights were monsters he had never fought before, golems of a higher species than the normal golems.
This would mean they would provide him with levels and stats. However, their numbers made it hard for Arthur to fight them alone, so it was good to have people who could distract some of the knights.
"What do you plan to do with that?" Ellen asked as she looked at the giant boar that Arthur had hunted earlier.