The retirement of your Artifact Weapon is coming closer. In the end of Legion your Artifact Weapon will retire its power and will be going away.
“I don’t want to spoil specifically what’s going to happen, but yes, your artifact weapon will not continue on in its current form,” he says. “We know that they need to go out with a bang, so to speak. These are some of the most powerful, iconic weapons in the world, and we can’t just have you replace them with a random plank with a nail in it.” – Hazzikostas (Polygon.com Interview)
Now WoWHead data mined a cinematic depicting their weapons soaking the corruption from the Dark Titan’s Blade:
But they also got a tip from MysticalOS “Your Artifact Weapons will gain “Instability” from the corruption, causing them to periodically lose Artifact Power. When the Instability effect is applied, your Artifact UI shakes and the Artifact Power total ticks down.”