The Darkheart (House Roof glitch)
 

A Glitch that makes DarkHeart (Boss Raider) at Padres del Fuego Beach never hit you while you hit him. Good for lvling grenade or dagger:

There is a two-story house to the right of Darkheart. Get under that house and jump twice and you are now on the roof of the house. Throw grenades at Darheart and you will see that as you hitting him, he just comes throws a dagger at you, switches to his sword and baddabin baddabum! happy lvling up!

This is a glitch if it even can be called that and not purposely made this way, that a lot of the bosses have. The bosses like this, tortuga swamp, Neban, Darkhart stop when switching to melee attack.

For Darkhart anywhere not just the roof, he will do this. He attacks, and when you keep him at a distance he throws dagger, move up closer he switches to melee and stays if he can't reach you.

Another post on this about Darkhart several posts down on this forum.