Those mysterious Odyssey Knights do not fight the wyverns merely to save the villagers (People of The Land). They fight because they want to die. When an Adventurer dies, they will see some flashbacks from their life in “real world” and they feel like they are back home during that time between dying and revival. That mysterious object they carry is a portable respawn point, so when they die, they will back to life nearby, so they can get killed again by the wyverns.
Interestingly, these people are doing this crazy act by choice. They are not mindless zombies without ability to think as human beings. They can still talk, they can argue. Tohya’s argument with one of them is a good way to show us a different side of this alternate world: not everyone can adjust to their new life in the new world. Some (many) of the Adventurers want to go home. This brings us to the most basic question throughout the series: why are they here?
Minori’s conversation with Roe 2 is very confusing. I don’t understand anything from it. If they are trying to make something mysterious so they can explain it later, they can do better than just spouting random staring-then-decide-not-to-talk scene. Log Horizon is USUALLY better than this.