The opening credits of Godzilla vs. Kong may hint at Mothra’s involvement in the original Titan War. Thousands of years ago, Godzilla’s ancestors waged war against Kong’s species somewhere in the Hollow Earth world. The Titan War was first teased in a painting that showed Godzilla and Kong fighting in Kong: Skull Island’s post-credits scene before it was shown again in Godzilla: King of the Monsters.
The idea that the two Titans had a history through their ancestors was reinforced by Godzilla vs. Kong. In the movie, Dr. Ilene Andrews (Rebecca Hall) spoke of a legend among the Iwi tribe about an ancient conflict between the two monster species. Exactly what happened has been left ambiguous, but it could be part of the reason why Godzilla is the last of his kind and why Kong’s race was forced to flee the Hollow Earth and make a new home on Skull Island.
It’s possible that other MonsterVerse Titans, like Mothra from King of the Monsters, participated in the Titan War. Interestingly, a cave painting in the opening credits shows a fight between four monsters. Three can be clearly identified: Godzilla, Kong, and a Skullcrawler. The fourth one pictured is a winged, insect-like creature that closely resembles Mothra. What this may indicate is that multiple Titan species may have played a part in the battle. After all, Godzilla vs. Kong never did specify that the Titan War was exclusive to their races. As rival alphas, they could have led diverse armies consisting of different kinds of monsters, including Mothra and the Skullcrawlers.
The painting shows the winged monster flying behind Godzilla, but it wasn’t made clear if it was attacking Godzilla or fighting on his side. If this panting really is a depiction of both Mothra and an ancient event in the MonsterVerse’s history, it seems likely that if she did choose a side, she’d take Godzilla’s. While the peaceful and benevolent Mothra seems better-suited for being a peacemaker or a neutral party, it may be that she was motivated to fight for one reason or another. She could have determined that Godzilla winning was the outcome that would best benefit the balance of nature.
Their connection is another factor that’s worth considering. It’s known that Godzilla and Mothra have a symbiotic relationship that extends back thousands of years. That has to be the case since it’s been confirmed that the egg in the Chinese temple was 10,000 years old. What happened in Mothra’s last life is hard to say, but it could be that at some point in her eternal life cycle of death and rebirth, Mothra helped Godzilla beat Kong’s ancestors and died in the process. If the MonsterVerse continues after Godzilla vs. Kong, a chance may present itself for Mothra’s role to be discussed. There’s still so much about her and her history that hasn’t been said on screen, so it does feel like something that could come up in Godzilla 3.