The Protector of the Plains is a boss enemy highly sought after by players for its loot. It is one of the Protectors, and carries a good amount of health with a high blockage chance.
Weak to: High damage
Deals: Slashing damage
Found at: Shrines (as an instanced boss) and nearby them as random encounter.
Drops: Each protector drops one item from the Protector set, look on the map and wiki for more information.
Strategy as Instance: You have to kill the prot in one go, if you run it will heal back, same strategy as below but without getting hit.
Strategy as encounter: The fight is very straight forward, by having no weakness, any high damage weapon works, but swords are recommended because of the good slashing resistances. The protector damage reduction goes from 20 all the way to 40 so the worse you weapon is, the longer it takes (and if it's plains or jungle protector the dura is wasted as chest and legs takes 80% of the hits). As for their weapon, they can be as bad as 2d10 x1 or as good as 3d13 x3 (which very very rarely happens), so heal often.
Reference Vocandin's Boss Hunting Guide for a comprehensive list of all bosses.