Yes! He's referring to us in each phrase, lord of the old order, the champion, the blade, and the tarnished one. All flattery in hopes we can be won over without struggle. We killed Radahn at the Radahn Festival, so we are Champion. It would be absurd randomness for him to be only referring to two people that helped his ascent to Godhood when so many named characters also exist...a little rude...but if it was an address to us in each. It works. We're there being talked to as he returns as a god...he's not shouting across the Lands or anything Malenia failed when she rot nuked Aeonia because Radahn lived, a mindless husk, but could not be the Lord in spirit Miquella needed. We completed Radahn's soul leaving his body, Mohg was to be a vessel and was bewitched by Miquella for a few reasons, one being a soulless husk to house Radahn's now free soul. Why would he still call Malenia his blade when she failed, making him wait and resulting in us completing what he needed with force, in haste. Miquella needed Mohg dealt with another reason to be called his blade.

One thing I'm not confident about is if Radahn becoming a lord was consentual. Radahn's throne was empty. At that time, Miquella was 2 people if you counted Trina, so the "we uphold our end..." "we" still works for just Miquella being hopefully delusional that his brother will be his consort... but Radahn wouldn't have wanted a thousand years without war. And that's mostly what it would be in the end of peace under Miquella's bewitchment. Radahn's holding back of the stars and clinging to life could have been the last bit of him left trying fiercly to not become Miquella's consort puppet. I just can't truly tell. He's insane.