This kind of makes me think of Seto and Nanaki. Seto being the 'protector' and Nanaki's familiarity and being stronger having fought alongside Avalanche.

I'm not sure where the 'guarding your gold' comes from though.

Though the way the riddle is structured it sounds like the the questions are being asked of Nanaki and Seto. Maybe by GI Nattak of the Gi tribe?

Past what I can call familiar,
Seto fought in the past, now Nanaki
There is a protector, the entrusted one,
But you are familiar as well.
Nanaki's similarity to the 'protector' Seto
I've fought you long ago, haven't I?
Again, a reference to Seto
Still guarding your gold, are you?
Gold could be a metaphor for his people. He still stands guard even though he was turned to stone
I'm stronger now, you know?
Tell me, though. What is your name?
Sounds like GI Nattak asking Nanaki's identity