The fics where Knuckles has some cool powers from the master emerald or is like a very special guy who talks to the master emerald are so good but I've been thinking. What if he isn't. He's the guardian of the master emerald, not a user. Sonic is the one who can use the chaos emeralds and is basically the chosen one when it come to chaos energy, and Knuckles just guards it.

I just imagine Knuckles, who's been put on angel island and basically sacrificed his entire life to this thing and never received any form of acknowledgment, who then meets Sonic who's basically a chaos energy magnet. Chaos emeralds love him, master emerald responds to him. Sonic is there to use the energy, Knuckles is to only guard it