the fact that river will go through unbearable pain fusing with gauis is part of the appeal.
river will suffer, badly, and in return ze gets what ze wants, which is to save others. its so simple compared to the confusing, meaningless suffering river experiences in mundane life that its irresistible to hir. the struggle gives river a single purpose, and a way to escape the complexity of existing. the pain is integral to the struggle, and is the selfish reward river receives for a deal that ze appears from an outside perspective get nothing out of.
nobody understands this except river and gaius themselves: the one thing they share in common is their attachment to pain, and their attachment for each other blooms from the pain their relationship causes. they are both getting exactly what they want from the other, which is to rip themselves to shreds forever.
