Masters for a match: the four sides red, green, blue and yellow (side 4 gets its own owner), and start_masters gives every master his core and his starting area

src/ui.rs

@@ -1300,6 +1300,7 @@ pub fn hover_info(g: &Game, ent: Option<usize>, tile: Option<(i32, i32)>) -> Vec
         Owner::Hero => "owner.hero",
         Owner::Rival1 => "owner.rival1",
         Owner::Rival2 => "owner.rival2",
+        Owner::Rival3 => "owner.rival3",
         Owner::None => "owner.none",
     };
     match t.kind {