Never Thought
Ryu laid out his terms very simply.
He wasn't a fool. There was a difference between entering the Tri Palace with a key versus entering without one. Though Ryu had, obviously, never entered personally. Considering he had targeted this Palace from the very beginning, how could he come without even this basic knowledge?
The Three Pupil Eclipse Sect definitely had a few keys with them. Ryu believed that they had three. It wouldn't make much sense for such a Sect to hand out the only Key they had just like that. However, more was always better.
Originally, the Three Pupil Eclipse Sect had sent out the key as a reward in order to balance a few things. Though they were the most powerful Sect, they were intelligent. Monopolizing the Palace for themselves would only lead to trouble. If wielding the strongest strength made one infallible, then there wouldn't be a history of rising and falling Clans and Sects.