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

lang/en.lang

@@ -604,6 +604,7 @@ msg.payday_walk = Payday! {0} creatures fetch their wages from the treasury ({1}
 msg.wage_unpaid = Your {0} found no gold for its wage and is furious!
 owner.rival1 = held by Mossgrim, the green master
 owner.rival2 = held by Lady Nightwell, the blue master
+owner.rival3 = held by the yellow master
 
 # rival masters (free game)
 newgame.difficulty = Opponents