[LTR] Implement The Balrog, Durin's Bane (#10515)

* [LTR] Implement The Balrog, Durin's Bane

I could use someone more experienced for this card:
Should the watcher `PermanentsSacrificedWatcher` be initialized locally in the card's class, or is a global initializing in GameImpl.java alright? I went for the latter for now, as my base for implementing the static cost reduction was Blood for the Blood God!

* apply review

* no longer instantiate watcher on every game.

Mage/src/main/java/mage/abilities/dynamicvalue/common/PermanentsSacrificedThisTurnCount.java

@@ -0,0 +1,40 @@
+
+package mage.abilities.dynamicvalue.common;
+
+import mage.abilities.Ability;
+import mage.abilities.dynamicvalue.DynamicValue;
+import mage.abilities.effects.Effect;
+import mage.game.Game;
+import mage.watchers.common.PermanentsSacrificedWatcher;
+
+/**
+ * @author Susucr
+ */
+public enum PermanentsSacrificedThisTurnCount implements DynamicValue {
+    instance;
+
+    @Override
+    public int calculate(Game game, Ability sourceAbility, Effect effect) {
+        PermanentsSacrificedWatcher watcher = game.getState().getWatcher(PermanentsSacrificedWatcher.class);
+        if (watcher != null) {
+            return watcher.getThisTurnSacrificedPermanents();
+        }
+        return 0;
+    }
+
+    @Override
+    public PermanentsSacrificedThisTurnCount copy() {
+        return PermanentsSacrificedThisTurnCount.instance;
+    }
+
+    @Override
+    public String toString() {
+        return "X";
+    }
+
+    @Override
+    public String getMessage() {
+        return "permanents sacrificed this turn";
+    }
+
+}

Mage/src/main/java/mage/abilities/hint/common/PermanentsSacrificedThisTurnHint.java

@@ -0,0 +1,28 @@
+package mage.abilities.hint.common;
+
+import mage.abilities.Ability;
+import mage.abilities.dynamicvalue.common.PermanentsSacrificedThisTurnCount;
+import mage.abilities.hint.Hint;
+import mage.abilities.hint.ValueHint;
+import mage.game.Game;
+
+/**
+ * @author Susucr
+ */
+public enum PermanentsSacrificedThisTurnHint implements Hint {
+    instance;
+
+    private static final Hint hint = new ValueHint(
+            "Permanents sacrificed this turn", PermanentsSacrificedThisTurnCount.instance
+    );
+
+    @Override
+    public String getText(Game game, Ability ability) {
+        return hint.getText(game, ability);
+    }
+
+    @Override
+    public PermanentsSacrificedThisTurnHint copy() {
+        return this;
+    }
+}

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

@@ -46,4 +46,8 @@ public class PermanentsSacrificedWatcher extends Watcher {
     public List<Permanent> getThisTurnSacrificedPermanents(UUID playerId) {
         return sacrificedPermanents.get(playerId);
     }
+
+    public int getThisTurnSacrificedPermanents() {
+        return sacrificedPermanents.values().stream().mapToInt(permanents -> permanents.size()).sum();
+    }
 }