[DFT] Implement Spikeshell Harrier

Mage/src/main/java/mage/players/PlayerImpl.java

@@ -4702,6 +4702,14 @@ public abstract class PlayerImpl implements Player, Serializable {
         }
     }
 
+    @Override
+    public void decreaseSpeed(Game game) {
+        if (speed > 1) {
+            speed--;
+            game.informPlayers(this.getLogName() + "'s speed has decreased to " + speed);
+        }
+    }
+
     @Override
     public boolean autoLoseGame() {
         return false;