Do you recognize this manwha ? HELP

Hii, i forgot the name of a manwha and can't seem to find it anywhere. VERY detailed description : It's about a guy born in a big family, evil one, who kept making heirs, he was really strong but ended up being killed, he was called the "loyal dog" of the family. He reincarnated as a baby, purposely fell into a special river during a test all the babies of the family have to go through (where they have to pick a sword in the "garden of a thousand swords" or smth) and got strong. Then he had a game-like interface with prizes when he did certain things. He grew up to be even stronger, went to a school under a false name, was killing demons undercover bc they plan to destroy the world, including a high priest who was actually a demon but he killed him with the help of a priestess that goes to the same school as him. There were levels he had to reach to be as strong as the head of a family, his dad was like a level 10 swormaster, he eventually got stronger. Oh, and he also lived in the forest for years, while everyone thought he had died, lost of girls like him, mostly a red headed girl who actually died but just came back to life thanks to him... Anyway, if someone remember it, PLEAAAASE help me!!! I think it was something like "The loyal dog of ..."