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/map.rs

@@ -145,9 +145,10 @@ pub enum Owner {
     Hero,
     Rival1, // AI dungeon masters (free play, campaign)
     Rival2,
+    Rival3, // the fourth master side: a third rival, or a human master in a match
 }
 
-const OWNERS: [Owner; 5] = [Owner::None, Owner::Player, Owner::Hero, Owner::Rival1, Owner::Rival2];
+const OWNERS: [Owner; 6] = [Owner::None, Owner::Player, Owner::Hero, Owner::Rival1, Owner::Rival2, Owner::Rival3];
 
 impl Owner {
     pub fn of_side(side: u8) -> Owner {
@@ -156,9 +157,14 @@ impl Owner {
             1 => Owner::Hero,
             2 => Owner::Rival1,
             3 => Owner::Rival2,
+            4 => Owner::Rival3,
             _ => Owner::None,
         }
     }
+
+    // the masters of a match: the four sides a dungeon master can play (1 is the heroes' side)
+    #[allow(dead_code)] // the sides of a match; the lobby (step C/D) uses them
+    pub const MASTER_SIDES: [u8; 4] = [0, 2, 3, 4];
 }
 
 // Short serde names (only used by version 1 savegames, newer ones use the packed codec)