One Piece has always been a series that builds toward shocking reveals, but the most recent spoiler might change the future of the Cross Guild forever. The mysterious grave related to the hero who fought Kaido and disappeared all along belonged to Kozuki Moria. This massive reveal connects Moria to the Kozuki bloodline, which lends itself to the possibility of Moria being related to Oden and even the uncle to Momonosuke and Hiyori.
In addition to the bloodline twist, this connection could mean Moria also knows how to read Poneglyphs, something that the Cross Guild is definitely lacking. Assuming he joins Crocodile and Mihawk, they might finally have a chance to fight the world to reach the One Piece.
Disclaimer: The article reflects the writer's opinion and includes spoilers from the One Piece manga.
How Moria could be the most important person the Cross Guild needs in One Piece, explained

Gecko Moria has been viewed since his first appearance as a fallen Warlord who never lived up to his potential, but his recent reveal as being a member of the Kozuki clan in chapter 1158, then his involvement in the story may be bigger than it's ever been before, particularly for the Cross Guild.
Crocodile, Mihawk, and Buggy have already made waves in the New World with a partnership based on power, fear, and ambition. Regardless of these three being extremely powerful, they have something critical missing in their quest for One Piece, which is the ability to read and interpret the Poneglyphs. And it is in this area that Moria, as a member of the Kozuki clan, may become the most important member of the crew.

The Kozuki clan's history cannot be disassociated with the Poneglyphs. For hundreds of years, the Kozuki family has followed and preserved the ancient language, and with Oden as part of Roger's crew, the former was vital in the latter's journey to Raftel. If Moria really and truly has Kozuki blood in him, then it is safe to say that Moria could either know this information or could at least have access to it.
That alone makes him invaluable. Crocodile and Mihawk are unmatched in brute strength and intelligence, but they cannot decode the road signs to the One Piece. Buggy inspires fear by reputation, but fear alone is not enough to take the ultimate treasure. Moria's heritage fills this gap perfectly.

Additionally, the Kozuki link gives political and symbolic significance to Moria's presence. Being related to Oden, he would personally link Cross Guild to Wano's heritage, a nation at the heart of the Void Century enigma.
This connection would grant them legitimacy to some allies and provide them with leverage against the World Government. It also suggests why Moria's survival following Kaido's collapse is significant; his information could shift the power balance.
If Moria enters the Cross Guild, they wouldn't simply be another violent faction; they would be major contenders for the final One Piece. The group would then possess brute force with Mihawk, cunning and drive with Crocodile, power with Buggy's reputation, and now, the secrets of history with Moria.
Final thoughts
Moria's surprising connection to the Kozuki clan could very well be the catalyst that turns the Cross Guild from a fearsome group into a legitimate force for attaining the One Piece.
His potential knowledge of the Poneglyphs closes the most crucial gap in the crew while additionally tying them to the legacy of Wano symbolically. Provided Mihawk's immediate strength, Crocodile's cunning, Buggy's influence, and Moria's lineage, the Cross Guild could be one of the best threats opposing the World Government.
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