Refactor: moved ManaPaidSourceWatcher to default watchers, added additional checks;

Mage.Sets/src/mage/cards/b/BergStrider.java

@@ -46,7 +46,7 @@ public final class BergStrider extends CardImpl {
         Ability ability = new EntersBattlefieldTriggeredAbility(new TapTargetEffect());
         ability.addEffect(new BergStriderEffect());
         ability.addTarget(new TargetPermanent(filter));
-        this.addAbility(ability, new ManaPaidSourceWatcher());
+        this.addAbility(ability);
     }
 
     private BergStrider(final BergStrider card) {

Mage.Sets/src/mage/cards/b/BlessingOfFrost.java

@@ -34,7 +34,6 @@ public final class BlessingOfFrost extends CardImpl {
 
         // Distribute X +1/+1 counters among any number of creatures you control, where X is the amount of {S} spent to cast this spell. Then draw a card for each creature you control with power 4 or greater.
         this.getSpellAbility().addEffect(new BlessingOfFrostEffect());
-        this.getSpellAbility().addWatcher(new ManaPaidSourceWatcher());
     }
 
     private BlessingOfFrost(final BlessingOfFrost card) {

Mage.Sets/src/mage/cards/b/BloodOnTheSnow.java

@@ -45,7 +45,6 @@ public final class BloodOnTheSnow extends CardImpl {
                 "Then return a creature or planeswalker card with mana value X or less"
                         + " from your graveyard to the battlefield, where X is the amount of {S} spent to cast this spell."
         );
-        this.getSpellAbility().addWatcher(new ManaPaidSourceWatcher());
     }
 
     private BloodOnTheSnow(final BloodOnTheSnow card) {

Mage.Sets/src/mage/cards/b/BorealOutrider.java

@@ -41,7 +41,7 @@ public final class BorealOutrider extends CardImpl {
                 ), BorealOutriderCondition.instance, "Whenever you cast a creature spell, " +
                 "if {S} of any of that spell's colors was spent to cast it, that creature " +
                 "enters the battlefield with an additional +1/+1 counter on it."
-        ), new ManaPaidSourceWatcher());
+        ));
     }
 
     private BorealOutrider(final BorealOutrider card) {

Mage.Sets/src/mage/cards/d/DevourIntellect.java

@@ -30,7 +30,6 @@ public final class DevourIntellect extends CardImpl {
                 TreasureSpentToCastCondition.instance,
                 "Target opponent discards a card. If mana from a Treasure was spent to cast this spell, instead that player reveals their hand, you choose a nonland card from it, then that player discards a card"
         ));
-        this.getSpellAbility().addWatcher(new ManaPaidSourceWatcher());
     }
 
     private DevourIntellect(final DevourIntellect card) {

Mage.Sets/src/mage/cards/f/ForswornPaladin.java

@@ -53,7 +53,7 @@ public final class ForswornPaladin extends CardImpl {
         );
         ability.addEffect(new ForswornPaladinEffect());
         ability.addTarget(new TargetCreaturePermanent());
-        this.addAbility(ability, new ManaPaidSourceWatcher());
+        this.addAbility(ability);
     }
 
     private ForswornPaladin(final ForswornPaladin card) {

Mage.Sets/src/mage/cards/g/GravenLore.java

@@ -25,7 +25,6 @@ public final class GravenLore extends CardImpl {
 
         // Scry X, where is the amount of {S} spent to cast this spell, then draw three cards.
         this.getSpellAbility().addEffect(new GravenLoreEffect());
-        this.getSpellAbility().addWatcher(new ManaPaidSourceWatcher());
     }
 
     private GravenLore(final GravenLore card) {

Mage.Sets/src/mage/cards/h/HiredHexblade.java

@@ -35,7 +35,7 @@ public final class HiredHexblade extends CardImpl {
                 "if mana from a Treasure was spent to cast it, you draw a card and you lose 1 life."
         );
         ability.addEffect(new LoseLifeSourceControllerEffect(1));
-        this.addAbility(ability, new ManaPaidSourceWatcher());
+        this.addAbility(ability);
     }
 
     private HiredHexblade(final HiredHexblade card) {

Mage.Sets/src/mage/cards/j/JadedSellSword.java

@@ -40,7 +40,7 @@ public final class JadedSellSword extends CardImpl {
         ability.addEffect(new GainAbilitySourceEffect(
                 HasteAbility.getInstance(), Duration.EndOfTurn
         ));
-        this.addAbility(ability, new ManaPaidSourceWatcher());
+        this.addAbility(ability);
     }
 
     private JadedSellSword(final JadedSellSword card) {

Mage.Sets/src/mage/cards/k/KalainReclusivePainter.java

@@ -38,7 +38,7 @@ public final class KalainReclusivePainter extends CardImpl {
         this.addAbility(new EntersBattlefieldTriggeredAbility(new CreateTokenEffect(new TreasureToken())));
 
         // Other creatures you control enter the battlefield with an additional +1/+1 counter on them for each mana from a Treasure spent to cast them.
-        this.addAbility(new SimpleStaticAbility(new KalainReclusivePainterEffect()), new ManaPaidSourceWatcher());
+        this.addAbility(new SimpleStaticAbility(new KalainReclusivePainterEffect()));
     }
 
     private KalainReclusivePainter(final KalainReclusivePainter card) {

Mage.Sets/src/mage/cards/p/PriceOfLoyalty.java

@@ -34,7 +34,6 @@ public final class PriceOfLoyalty extends CardImpl {
         ).setText("It gains haste until end of turn."));
         this.getSpellAbility().addEffect(new PriceOfLoyaltyEffect());
         this.getSpellAbility().addTarget(new TargetCreaturePermanent());
-        this.getSpellAbility().addWatcher(new ManaPaidSourceWatcher());
     }
 
     private PriceOfLoyalty(final PriceOfLoyalty card) {

Mage.Sets/src/mage/cards/s/SearchForGlory.java

@@ -42,7 +42,6 @@ public final class SearchForGlory extends CardImpl {
         this.getSpellAbility().addEffect(new GainLifeEffect(
                 SnowManaSpentValue.instance
         ).setText("You gain 1 life for each {S} spent to cast this spell"));
-        this.getSpellAbility().addWatcher(new ManaPaidSourceWatcher());
     }
 
     private SearchForGlory(final SearchForGlory card) {

Mage.Sets/src/mage/cards/s/SpoilsOfTheHunt.java

@@ -32,7 +32,6 @@ public final class SpoilsOfTheHunt extends CardImpl {
         ));
         this.getSpellAbility().addTarget(new TargetControlledCreaturePermanent());
         this.getSpellAbility().addTarget(new TargetOpponentsCreaturePermanent());
-        this.getSpellAbility().addWatcher(new ManaPaidSourceWatcher());
     }
 
     private SpoilsOfTheHunt(final SpoilsOfTheHunt card) {

Mage/src/main/java/mage/game/GameImpl.java

@@ -64,6 +64,8 @@ import mage.util.GameLog;
 import mage.util.MessageToClient;
 import mage.util.RandomUtil;
 import mage.util.functions.CopyApplier;
+import mage.watchers.Watcher;
+import mage.watchers.Watchers;
 import mage.watchers.common.*;
 import org.apache.log4j.Logger;
 
@@ -1185,18 +1187,29 @@ public abstract class GameImpl implements Game, Serializable {
     }
 
     public void initGameDefaultWatchers() {
-        getState().addWatcher(new MorbidWatcher());
+        List<Watcher> newWatchers = new ArrayList<>();
-        getState().addWatcher(new CastSpellLastTurnWatcher());
+        newWatchers.add(new MorbidWatcher());
-        getState().addWatcher(new CastSpellYourLastTurnWatcher());
+        newWatchers.add(new CastSpellLastTurnWatcher());
-        getState().addWatcher(new PlayerLostLifeWatcher());
+        newWatchers.add(new CastSpellYourLastTurnWatcher());
-        getState().addWatcher(new PlayerLostLifeNonCombatWatcher());
+        newWatchers.add(new PlayerLostLifeWatcher());
-        getState().addWatcher(new BlockedAttackerWatcher());
+        newWatchers.add(new PlayerLostLifeNonCombatWatcher());
-        getState().addWatcher(new DamageDoneWatcher());
+        newWatchers.add(new BlockedAttackerWatcher());
-        getState().addWatcher(new PlanarRollWatcher());
+        newWatchers.add(new DamageDoneWatcher());
-        getState().addWatcher(new AttackedThisTurnWatcher());
+        newWatchers.add(new PlanarRollWatcher());
-        getState().addWatcher(new PlayersAttackedThisTurnWatcher());
+        newWatchers.add(new AttackedThisTurnWatcher());
-        getState().addWatcher(new CardsDrawnThisTurnWatcher());
+        newWatchers.add(new PlayersAttackedThisTurnWatcher());
-        getState().addWatcher(new ManaSpentToCastWatcher());
+        newWatchers.add(new CardsDrawnThisTurnWatcher());
+        newWatchers.add(new ManaSpentToCastWatcher());
+        newWatchers.add(new ManaPaidSourceWatcher());
+
+        // runtime check - allows only GAME scope (one watcher per game)
+        newWatchers.forEach(watcher -> {
+            if (watcher.getScope().equals(WatcherScope.GAME)) {
+                throw new IllegalStateException("Game default watchers must have GAME scope: " + watcher.getClass().getCanonicalName());
+            }
+        });
+
+        newWatchers.forEach(getState()::addWatcher);
     }
 
     public void initPlayerDefaultWatchers(UUID playerId) {

Mage/src/main/java/mage/watchers/Watcher.java

@@ -169,4 +169,7 @@ public abstract class Watcher implements Serializable {
         return null;
     }
 
+    public WatcherScope getScope() {
+        return scope;
+    }
 }

Mage/src/main/java/mage/watchers/common/ManaPaidSourceWatcher.java

@@ -19,6 +19,8 @@ import java.util.Map;
 import java.util.UUID;
 
 /**
+ * Default watcher, no needs to add it to ability
+ *
  * @author TheElk801
  */
 public class ManaPaidSourceWatcher extends Watcher {