So this is a fantasy novel about a epic war, as usual. My world consists of 3 realms - 2 of them are active and 1 of them is a mystery. The 2 active realms are the Underworld and the realm of the living (don't have a good name yet)
Now my MC has some special powers that everyone wants. So to cut to the chase - this is now the penultimate arch just before the ending of the novel. My villain kidnaps my MC's lover, and threatens to kill her unless he breaks down the barriers between the 2 realms, which would have the effect of allowing the enemy to flood the living realm with his shadow army of underworld monsters from more points across the living realm, allowing him to take down a pretty important city (since one of the divides is within this city), which would lead the villain to being able to take down the capital, which would be the final defeat of the living.
So my MC agrees, in order to save his lover, with the hope of fixing this later.
Logical? Stupid? Would it make you despise my MC? Note - he knows it's nothing good but he's not 100% sure of the consequences of breaking down the barriers. He's a smart guy but without formal education and certainly know little about these "spiritual matters/existences".