Oregon has no duty to retreat. The use of force for self defense can only be used, when it is reasonably believed that it is needed to prevent immediate harm. This applies to defense of one's self or defense of a third party. The force used for self defense, must be proportional to the believed force that the aggressor would have used.
Deadly force can only be used to defend one's self when it is believed that there is an immediate threat of a forcible felony. Or when the aggressor is "about to use unlawful deadly physical force against a person." ORS 161.219
Castle Laws are laws that address the use of force when defending one's self inside their home, or on their property. Some states expand this to vehicles, and the person's place of work. Castle Laws generally include: the places where this law applies, the requirements fro use of deadly force, if there is a duty to retreat, the amount of force that maybe used in defending one's self or others. These vary widely from state to state.