At first, I thought Ripley was a slave the Celestial Dragons were going to kill off on God Valley, who got rescued by Gyaban. Ripley is 80 in the current story: she would have been 42 on God Valley.
Since Oda likes his age gaps, I thought Ripley would fall in love with Gyaban, but he would reject her, since a 42-year-old Giant is like a human 14-year-old, and then Gyaban would meet her like two decades later in Elbaph, when she would be the human equivalent of in her 20s.
In this case, though, it would be more of a "snuck aboard the ship", theory:
Ripley and Loki, both wanting to explore the world, and wanting to help Harald's friend, Rocks, snuck onto Harald's ship, when Harald sailed to God Valley to help Rocks. I believe we'll see Harald in the next several chapters, as him arriving after Rocks' is Domi Reversi'd fits their very tragic friendship, and Harald being the one to actually kill Domi Rocks would totally explain Harald ripping his horns out.
He was forced to murder the friend he betrayed, after choosing literally Satan over Rocks, and doing so led to Rocks' homeland being genocided, and his wife most likely being murdered.
In this case, Ripley and Loki would be like Dragon, just kind of screwing around not knowing what the hell they got themselves into, and Ripley would get saved by Gyaban, fall for him, then confess to him years later on Elbaph.
So, this theory now hinges on Harald arriving to Elbaph to try to help Rocks.
I think Roger and Garp end up fighting Imu-Saturn, that's the enemy they've both been focused on. RoGarp def clash with Domi Rocks, but I honestly don't think anyone we've seen but Harald in the verse can actually kill Rocks at this point in the story. Even Imu couldn't kill him, Rocks stated Imu's attack didn't hurt him.
Would be really cool if Ripley can damage the God's Knights on Elbaph, and learned the tech from Gyaban.