diff --git a/Mage.Sets/src/mage/cards/d/DreamThief.java b/Mage.Sets/src/mage/cards/d/DreamThief.java
index 79338e861ce..d8d5364b3f8 100644
--- a/Mage.Sets/src/mage/cards/d/DreamThief.java
+++ b/Mage.Sets/src/mage/cards/d/DreamThief.java
@@ -27,6 +27,7 @@
  */
 package mage.cards.d;
 
+import java.util.List;
 import java.util.UUID;
 import mage.MageInt;
 import mage.abilities.Ability;
@@ -52,7 +53,7 @@ public class DreamThief extends CardImpl {
     private static final String rule = "draw a card if you've cast another blue spell this turn";
 
     public DreamThief(UUID ownerId, CardSetInfo setInfo) {
-        super(ownerId,setInfo,new CardType[]{CardType.CREATURE},"{2}{U}");
+        super(ownerId, setInfo, new CardType[]{CardType.CREATURE}, "{2}{U}");
         this.subtype.add(SubType.FAERIE);
         this.subtype.add(SubType.ROGUE);
 
@@ -84,9 +85,12 @@ class CastBlueSpellThisTurnCondition implements Condition {
     public boolean apply(Game game, Ability source) {
         SpellsCastWatcher watcher = (SpellsCastWatcher) game.getState().getWatchers().get(SpellsCastWatcher.class.getSimpleName());
         if (watcher != null) {
-            for (Spell spell : watcher.getSpellsCastThisTurn(source.getControllerId())) {
-                if (!spell.getSourceId().equals(source.getSourceId()) && spell.getColor(game).isBlue()) {
-                    return true;
+            List<Spell> spells = watcher.getSpellsCastThisTurn(source.getControllerId());
+            if (spells != null) {
+                for (Spell spell : spells) {
+                    if (!spell.getSourceId().equals(source.getSourceId()) && spell.getColor(game).isBlue()) {
+                        return true;
+                    }
                 }
             }
         }
diff --git a/Mage.Sets/src/mage/cards/p/Panharmonicon.java b/Mage.Sets/src/mage/cards/p/Panharmonicon.java
index 4bade4472d6..26dfcafdf5e 100644
--- a/Mage.Sets/src/mage/cards/p/Panharmonicon.java
+++ b/Mage.Sets/src/mage/cards/p/Panharmonicon.java
@@ -50,7 +50,7 @@ import mage.game.events.NumberOfTriggersEvent;
 public class Panharmonicon extends CardImpl {
 
     public Panharmonicon(UUID ownerId, CardSetInfo setInfo) {
-        super(ownerId,setInfo,new CardType[]{CardType.ARTIFACT},"{4}");
+        super(ownerId, setInfo, new CardType[]{CardType.ARTIFACT}, "{4}");
 
         // If an artifact or creature entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
         this.addAbility(new SimpleStaticAbility(Zone.BATTLEFIELD, new PanharmoniconEffect()));
@@ -95,7 +95,9 @@ class PanharmoniconEffect extends ReplacementEffectImpl {
             if (source.getControllerId().equals(event.getPlayerId())) {
                 GameEvent sourceEvent = numberOfTriggersEvent.getSourceEvent();
                 // Only EtB triggers
-                if (sourceEvent.getType() == EventType.ENTERS_THE_BATTLEFIELD && sourceEvent instanceof EntersTheBattlefieldEvent) {
+                if (sourceEvent != null
+                        && sourceEvent.getType() == EventType.ENTERS_THE_BATTLEFIELD
+                        && sourceEvent instanceof EntersTheBattlefieldEvent) {
                     EntersTheBattlefieldEvent entersTheBattlefieldEvent = (EntersTheBattlefieldEvent) sourceEvent;
                     // Only for entering artifacts or creatures
                     if (entersTheBattlefieldEvent.getTarget().isArtifact()
@@ -116,4 +118,4 @@ class PanharmoniconEffect extends ReplacementEffectImpl {
         event.setAmount(event.getAmount() + 1);
         return false;
     }
-}
\ No newline at end of file
+}
diff --git a/Mage.Sets/src/mage/cards/t/TreacherousPitDweller.java b/Mage.Sets/src/mage/cards/t/TreacherousPitDweller.java
index aeb1ccac8f9..16429b4734f 100644
--- a/Mage.Sets/src/mage/cards/t/TreacherousPitDweller.java
+++ b/Mage.Sets/src/mage/cards/t/TreacherousPitDweller.java
@@ -29,6 +29,7 @@ package mage.cards.t;
 
 import java.util.UUID;
 import mage.MageInt;
+import mage.MageObject;
 import mage.abilities.Ability;
 import mage.abilities.TriggeredAbilityImpl;
 import mage.abilities.effects.ContinuousEffectImpl;
@@ -49,7 +50,7 @@ import mage.target.common.TargetOpponent;
 public class TreacherousPitDweller extends CardImpl {
 
     public TreacherousPitDweller(UUID ownerId, CardSetInfo setInfo) {
-        super(ownerId,setInfo,new CardType[]{CardType.CREATURE},"{B}{B}");
+        super(ownerId, setInfo, new CardType[]{CardType.CREATURE}, "{B}{B}");
         this.subtype.add(SubType.DEMON);
 
         this.power = new MageInt(4);
@@ -77,24 +78,24 @@ class TreacherousPitDwellerTriggeredAbility extends TriggeredAbilityImpl {
     private static final String ruleText = "When {this} enters the battlefield from a graveyard, ";
 
     public TreacherousPitDwellerTriggeredAbility() {
-        super(Zone.BATTLEFIELD, new TreacherousPitDwellerEffect(),false);
+        super(Zone.BATTLEFIELD, new TreacherousPitDwellerEffect(), false);
         addTarget(new TargetOpponent());
     }
 
     public TreacherousPitDwellerTriggeredAbility(final TreacherousPitDwellerTriggeredAbility ability) {
         super(ability);
     }
-    
+
     @Override
     public boolean checkEventType(GameEvent event, Game game) {
         return event.getType() == GameEvent.EventType.ENTERS_THE_BATTLEFIELD;
     }
-    
+
     @Override
     public boolean checkTrigger(GameEvent event, Game game) {
-        return  event.getTargetId().equals(getSourceId()) && ((EntersTheBattlefieldEvent) event).getFromZone() == Zone.GRAVEYARD;
-    }    
-    
+        return event.getTargetId().equals(getSourceId()) && ((EntersTheBattlefieldEvent) event).getFromZone() == Zone.GRAVEYARD;
+    }
+
     @Override
     public TreacherousPitDwellerTriggeredAbility copy() {
         return new TreacherousPitDwellerTriggeredAbility(this);
@@ -104,7 +105,7 @@ class TreacherousPitDwellerTriggeredAbility extends TriggeredAbilityImpl {
     public String getRule() {
         return ruleText + super.getRule();
     }
-    
+
 }
 
 class TreacherousPitDwellerEffect extends ContinuousEffectImpl {
@@ -125,10 +126,12 @@ class TreacherousPitDwellerEffect extends ContinuousEffectImpl {
 
     @Override
     public boolean apply(Game game, Ability source) {
-        Permanent permanent = (Permanent) source.getSourceObjectIfItStillExists(game);
+        MageObject permanent = source.getSourceObjectIfItStillExists(game); // it can also return Card object
         Player targetOpponent = game.getPlayer(source.getFirstTarget());
-        if (permanent != null && targetOpponent != null) {
-            return permanent.changeControllerId(targetOpponent.getId(), game);
+        if (permanent != null
+                && (permanent instanceof Permanent)
+                && targetOpponent != null) {
+            return ((Permanent) permanent).changeControllerId(targetOpponent.getId(), game);
         } else {
             discard();
         }