Oath: the Fearless Sword

[Traditional western fantasy, time travel, low magic, protagonist warrior, revenge + conquest, as serious as possible] He was once a social animal from another world, He is a low-key and taciturn servant, He is an illegitimate child that everyone despises, He lost everything under the enemy's sword, A vow made in despair and pain. When he is reborn in the blood and soil, He is determined and determined to take revenge. Holding the fearless sword, you will be invincible.