ok I have quick question about Archfiend oath and it coming in the from of an example so keep with me here ok.

Lets say I have Archfiend oath face up on the field and active it effect by paying 500 life points lets say I then active giant trunade and everything resolving with Archfiend oath first of course. Then Archfiend oath returns to my hand can active Archfiend oath again and use effect again on the same turn?

I know this may be a dumb question but want I make sure I know everything about this card before I try to make a deck base around. Thank you for your time

Yes...since returning it to your hand "Reset" it and the "once per turn" effect only applies while it's still face-up on the field. So it's basically like using a second one.

that what i thought thank you for clearing it up