Alright then. Thanks.
It is in Legend of Camelot, Chapter 5 : Jor is talking to Merlin ""This is the third time we meet, eldest god," said the World Serpent. "There shall not be a fourth."
Then later, you have this dialogue :
"Did you ever wonder how I was able to hide my power from you, all those eons ago?" Merlin bared his teeth in a predatory grin. "I am not the only thing that survived the last turn of your great wheel. All the power of my kin, all that I could save in that last moment, was too much to take within myself. Even a god could not have withstood that. So like a diamond I crushed it into the physical realm, and when time began anew, I forged it into that blade."
Arthur shot Merlin a glance, the shock of revelation clear upon his face. After all this time, he had never known the true nature of the blade he carried.
"I kept it hidden, locked away for so long, waiting for the day I would find the one who was worthy to wield it. The one slayer who had the power to use Excalibur, and strike you down when you returned."
Jormungandr loosed a roar, sending a cyclone of snow and dust lashing over Merlin and the other gods. They stood their ground amidst the tempest, glaring back at the enraged dragon looming over them.
"Deceit," Jormungandr spat. "Lies and trickery. You were always a creature of shadow and falsehood, eldest god. And even if your words are true, my power is too great. You might thank your fellows here for bestowing Ragnarok upon me, with it there is no force in creation that can stop the cycle from turning."