Lindwurm is rather bitter and distant from the world, being born a bastard child and cursed due to his mother's selfishness and mistakes. All of his life, he was treated as a nuisance and monster, and so his older half sister, Alice,  was the only one who made him feel something closed to love (though even her love could get sadistic). So his views can be a bit skewed as to what is healthy and happy.

He was born looking like a dragon, though he shortly after took a humanoid form with the features of a dragon still in tact (scales, tail, etc). Early in his childhood, Alice ended up making him a potion to help mask his form and make him appear human. He also has a full dragon form that he can unlock, though he tends not to use it (though it can be triggered from high levels of stress). Not even Rampion has seen him outside of his human form, as he is very ashamed as to what he truly looks like.

His main reason for feeling disdain for Rampion is jealousy over how Alice, his own blood seems to love and care for her adoptive child more than him. It also muddies the water that he feels attraction for her and he doesn't know how to deal with it, especially since he assumes that everyone and anyone would reject him if they saw his true form.