BestDebaterEver
Head of Debate Club
The key things that hasn't been mentioned in combination yet are:
1. Celeste was able to freely draw power from Muur in addition to her own. The only "conflict" was that she chose not to do this earlier in the fight.
2. Muur did not "take over" at the end; they joined their powers in perfect unison, as is indicated by the merging dialogue.
https://i.imgur.com/2kDwXSK.jpg
This is made abundantly clear by the fact immediately after the fight, Morne is in perfect control of herself. She allowed Muur a degree of control so that they could increase their combined power.
https://2.bp.blogspot.com/6JkcnYf1eSRQr3GwYaPRvzzQXoQEGC89NZDLusXPONNh3YC_J-QVqueO_3l4XlUO16s0ExjsvAg=s0
The ideas that:
1. Morne is hindered by Muur's presence, when she draw on his power freely.
and
2. Morne and Muur are capped at the "host's level", and did not combine their powers.
...is unsupported by the comic.
If someone wants to argue that:
Karness Muur body and spirit > Celeste Morne body and spirit + Muur's spirit.
You can go ahead and do that, but until you actually prove that as a rule, I am not inclined to agree that, as a rule, Muur was more powerful in ancient times than he was at the apex of the battle in Vector.