* Cost reduction effects - fixed that some cards with cost reduction can't be played (example: Price of Fame, see #6685, #6684);

Mage.Sets/src/mage/cards/m/MysticalDispute.java

@@ -1,7 +1,5 @@
 package mage.cards.m;
 
-import java.util.Collection;
-import java.util.UUID;
 import mage.abilities.Ability;
 import mage.abilities.common.SimpleStaticAbility;
 import mage.abilities.condition.Condition;
@@ -17,6 +15,9 @@ import mage.game.stack.StackObject;
 import mage.target.Target;
 import mage.target.TargetSpell;
 
+import java.util.Collection;
+import java.util.UUID;
+
 /**
  * @author TheElk801
  */
@@ -27,7 +28,7 @@ public final class MysticalDispute extends CardImpl {
 
         // This spell costs {2} less to cast if it targets a blue spell.
         this.addAbility(new SimpleStaticAbility(
-                Zone.ALL, new SpellCostReductionSourceEffect(2, MysticalDisputeCondition.instance)
+                Zone.ALL, new SpellCostReductionSourceEffect(2, MysticalDisputeCondition.instance).setCanWorksOnStackOnly(true)
         ).setRuleAtTheTop(true));
 
         // Counter target spell unless its controller pays {3}.

Mage.Sets/src/mage/cards/n/NotOfThisWorld.java

@@ -1,7 +1,5 @@
 package mage.cards.n;
 
-import java.util.Collection;
-import java.util.UUID;
 import mage.abilities.Ability;
 import mage.abilities.Mode;
 import mage.abilities.common.SimpleStaticAbility;
@@ -21,6 +19,9 @@ import mage.game.stack.StackObject;
 import mage.target.Target;
 import mage.target.TargetStackObject;
 
+import java.util.Collection;
+import java.util.UUID;
+
 /**
  * @author Rafbill
  */
@@ -41,7 +42,7 @@ public final class NotOfThisWorld extends CardImpl {
         this.getSpellAbility().addTarget(new TargetStackObject(filter));
 
         // Not of This World costs {7} less to cast if it targets a spell or ability that targets a creature you control with power 7 or greater.
-        this.addAbility(new SimpleStaticAbility(Zone.ALL, new SpellCostReductionSourceEffect(7, NotOfThisWorldCondition.instance)));
+        this.addAbility(new SimpleStaticAbility(Zone.ALL, new SpellCostReductionSourceEffect(7, NotOfThisWorldCondition.instance).setCanWorksOnStackOnly(true)));
     }
 
     private NotOfThisWorld(final NotOfThisWorld card) {
@@ -86,8 +87,8 @@ enum NotOfThisWorldCondition implements Condition {
                 .flatMap(Collection::stream)
                 .map(game::getPermanentOrLKIBattlefield)
                 .anyMatch(permanent -> permanent != null && filter.match(
-                permanent, sourceSpell.getSourceId(), sourceSpell.getControllerId(), game
-        ));
+                        permanent, sourceSpell.getSourceId(), sourceSpell.getControllerId(), game
+                ));
     }
 
     @Override

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

@@ -1,6 +1,5 @@
 package mage.cards.p;
 
-import java.util.UUID;
 import mage.abilities.common.SimpleStaticAbility;
 import mage.abilities.condition.Condition;
 import mage.abilities.condition.common.SourceTargetsPermanentCondition;
@@ -16,6 +15,8 @@ import mage.filter.FilterPermanent;
 import mage.filter.common.FilterCreaturePermanent;
 import mage.target.common.TargetCreaturePermanent;
 
+import java.util.UUID;
+
 /**
  * @author TheElk801
  */
@@ -35,7 +36,7 @@ public final class PriceOfFame extends CardImpl {
 
         // This spell costs {2} less to cast if it targets a legendary creature.
         this.addAbility(new SimpleStaticAbility(
-                Zone.ALL, new SpellCostReductionSourceEffect(2, condition)
+                Zone.ALL, new SpellCostReductionSourceEffect(2, condition).setCanWorksOnStackOnly(true)
         ).setRuleAtTheTop(true));
 
         // Destroy target creature.

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

@@ -1,6 +1,5 @@
 package mage.cards.s;
 
-import java.util.UUID;
 import mage.abilities.common.SimpleStaticAbility;
 import mage.abilities.condition.Condition;
 import mage.abilities.condition.common.SourceTargetsPermanentCondition;
@@ -20,6 +19,8 @@ import mage.filter.common.FilterControlledCreaturePermanent;
 import mage.target.common.TargetControlledCreaturePermanent;
 import mage.target.common.TargetCreaturePermanent;
 
+import java.util.UUID;
+
 /**
  * @author TheElk801
  */
@@ -35,7 +36,7 @@ public final class SavageStomp extends CardImpl {
 
         // Savage Stomp costs {2} less to cast if it targets a Dinosaur you control.
         this.addAbility(new SimpleStaticAbility(
-                Zone.ALL, new SpellCostReductionSourceEffect(2, condition)
+                Zone.ALL, new SpellCostReductionSourceEffect(2, condition).setCanWorksOnStackOnly(true)
         ).setRuleAtTheTop(true));
 
         // Put a +1/+1 counter on target creature you control. Then that creature fights target creature you don't control.

Mage.Tests/src/test/java/org/mage/test/cards/cost/modification/CostReduceWithConditionTest.java

@@ -2,14 +2,13 @@ package org.mage.test.cards.cost.modification;
 
 import mage.constants.PhaseStep;
 import mage.constants.Zone;
-import org.junit.Ignore;
 import org.junit.Test;
-import org.mage.test.serverside.base.CardTestPlayerBase;
+import org.mage.test.serverside.base.CardTestPlayerBaseWithAIHelps;
 
 /**
  * @author JayDi85
  */
-public class CostReduceWithConditionTest extends CardTestPlayerBase {
+public class CostReduceWithConditionTest extends CardTestPlayerBaseWithAIHelps {
 
     @Test
     public void test_PriceOfFame_Normal() {
@@ -31,9 +30,9 @@ public class CostReduceWithConditionTest extends CardTestPlayerBase {
     }
 
     @Test
-    @Ignore
-    // TODO: implement workaround like putToStackAsNonPlayable for abilities, see https://github.com/magefree/mage/issues/6685
-    public void test_PriceOfFame_Reduce() {
+    public void test_PriceOfFame_Reduce_Manual() {
+        // https://github.com/magefree/mage/issues/6685
+
         // {3}{B}
         // This spell costs {2} less to cast if it targets a legendary creature.
         // Destroy target creature.
@@ -50,4 +49,26 @@ public class CostReduceWithConditionTest extends CardTestPlayerBase {
 
         assertGraveyardCount(playerB, "Anje Falkenrath", 1);
     }
+
+    @Test
+    public void test_PriceOfFame_Reduce_AI() {
+        // https://github.com/magefree/mage/issues/6685
+
+        // {3}{B}
+        // This spell costs {2} less to cast if it targets a legendary creature.
+        // Destroy target creature.
+        addCard(Zone.HAND, playerA, "Price of Fame", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Swamp", 4 - 2);
+        addCard(Zone.BATTLEFIELD, playerB, "Anje Falkenrath", 1);
+
+        // AI must see and play that cards too
+        aiPlayPriority(1, PhaseStep.PRECOMBAT_MAIN, playerA);
+
+        setStrictChooseMode(true);
+        setStopAt(1, PhaseStep.BEGIN_COMBAT);
+        execute();
+        assertAllCommandsUsed();
+
+        assertGraveyardCount(playerB, "Anje Falkenrath", 1);
+    }
 }

Mage/src/main/java/mage/abilities/effects/common/cost/CostModificationEffectImpl.java

@@ -1,27 +1,28 @@
-
-
 package mage.abilities.effects.common.cost;
 
-import mage.constants.Duration;
-import mage.constants.EffectType;
-import mage.constants.Outcome;
 import mage.abilities.Ability;
 import mage.abilities.effects.ContinuousEffectImpl;
 import mage.abilities.effects.CostModificationEffect;
 import mage.constants.CostModificationType;
+import mage.constants.Duration;
+import mage.constants.EffectType;
+import mage.constants.Outcome;
 import mage.game.Game;
 
 /**
  * Simple implementation of a {@link CostModificationEffect} offering simplified
  * construction to setup the object for use by the mage framework.
-
+ *
  * @author maurer.it_at_gmail.com
  */
 public abstract class CostModificationEffectImpl extends ContinuousEffectImpl implements CostModificationEffect {
 
     private final CostModificationType modificationType;
-    
-    public CostModificationEffectImpl ( Duration duration, Outcome outcome, CostModificationType type) {
+
+    // if effect need real stack object to check then mark it as stack only (example: apply cost reduction if you target human creature)
+    private boolean worksOnStackOnly = false;
+
+    public CostModificationEffectImpl(Duration duration, Outcome outcome, CostModificationType type) {
         super(duration, outcome);
         this.effectType = EffectType.COSTMODIFICATION;
         this.modificationType = type;
@@ -30,23 +31,33 @@ public abstract class CostModificationEffectImpl extends ContinuousEffectImpl im
     public CostModificationEffectImpl(final CostModificationEffectImpl effect) {
         super(effect);
         this.modificationType = effect.modificationType;
+        this.worksOnStackOnly = effect.worksOnStackOnly;
     }
 
     /**
      * Overridden and 'no-op' implementation put in place.
      *
-     * @see #apply(mage.game.Game, mage.abilities.Ability, mage.abilities.Ability)
-     *
      * @param game
      * @param source
      * @return
+     * @see #apply(mage.game.Game, mage.abilities.Ability, mage.abilities.Ability)
      */
     @Override
-    public final boolean apply ( Game game, Ability source ) { return false; }
-       
+    public final boolean apply(Game game, Ability source) {
+        return false;
+    }
+
     @Override
-    public CostModificationType getModificationType(){
+    public CostModificationType getModificationType() {
         return this.modificationType;
     }
 
+    public CostModificationEffectImpl setCanWorksOnStackOnly(boolean worksOnStackOnly) {
+        this.worksOnStackOnly = worksOnStackOnly;
+        return this;
+    }
+
+    public boolean canWorksOnStackOnly() {
+        return this.worksOnStackOnly;
+    }
 }

Mage/src/main/java/mage/abilities/effects/common/cost/SpellCostReductionSourceEffect.java

@@ -93,7 +93,9 @@ public class SpellCostReductionSourceEffect extends CostModificationEffectImpl {
     @Override
     public boolean applies(Ability abilityToModify, Ability source, Game game) {
         if (abilityToModify.getSourceId().equals(source.getSourceId()) && (abilityToModify instanceof SpellAbility)) {
-            return condition == null || condition.apply(game, source);
+            // some conditions can works after put on stack, so skip it in get playable (allows user to put card on stack anyway)
+            boolean skipCondition = game.inCheckPlayableState() && canWorksOnStackOnly();
+            return condition == null || skipCondition || condition.apply(game, source);
         }
         return false;
     }