A priest will stand by the side of the road, urging you to listen to his praise of Trinimac. If you have the Mages Guild Persuasive Will perk, you may persuade the priest into giving you Trinimac's Blessing, increasing your critical chance by 1% for 30 minutes.
Conversely, you may also find a Priest of Malacath. Talking to him with the Fighters Guild Intimidating Presence perk will give you the Malacath's Blessing, increasing your critical resistance by 1% for 30 minutes.
If you're on PC you can use the Locations add-on to mark them all on the map.
If you're not on PC and need an image provided I will do one tonight when I am at my PC. Although they might be available on Google images.
Note that many events share the same spawn location so it's random as to which one (if any) you get when you visit a location.