I'd like to know the whole sentence because the の doesn't make sense.

Suppose the の is merely a typo, 

>その自重を支える翼持つ「冒険者」よ 

means:

>***Hey, the "adventurers" who have the wings to support their weight, ...***

In this context, it's obvious that


**自重（じじゅう）= the weight of oneself = one's weight** .

自重（じちょう）する means to "to take good care of oneself" and it doesn't fit in this context.