Step back, we have an Angry Panda here! Those things are killing machines. Didn't you watch Kung Fu Panda?

In a more serious note, this has been mentioned in the board before. They don't plan on giving you the mantles because you had your inventory full.

Advice: always keep free slots in your inventory. Or Odin Mantles, like me.

By the way, how do we get Gold? I was tanking Odin for some five minutes, didn't die and I only got Silver.