* Deranged Assistant - Disallowed possible undo to prevent cheating with otherwise hidden information (top card of library).

Mage.Sets/src/mage/sets/dragonsmaze/RotFarmSkeleton.java

@@ -53,13 +53,13 @@ public class RotFarmSkeleton extends CardImpl {
         this.expansionSetCode = "DGM";
         this.subtype.add("Plant");
         this.subtype.add("Skeleton");
-        this.color.setBlack(true);
-        this.color.setGreen(true);
+
         this.power = new MageInt(4);
         this.toughness = new MageInt(1);
 
         // Rot Farm Skeleton can't block.
         this.addAbility(new CantBlockAbility());
+        
         // 2{B}{G}, Put the top four cards of your library into your graveyard: Return Rot Farm Skeleton from your graveyard to the battlefield. Activate this ability only any time you could cast a sorcery.
         Ability ability = new ActivateAsSorceryActivatedAbility(Zone.GRAVEYARD, new ReturnSourceFromGraveyardToBattlefieldEffect(), new ManaCostsImpl("{2}{B}{G}"));
         ability.addCost(new PutTopCardOfYourLibraryToGraveyardCost(4));

Mage.Sets/src/mage/sets/innistrad/DerangedAssistant.java

@@ -47,13 +47,13 @@ public class DerangedAssistant extends CardImpl {
         this.subtype.add("Human");
         this.subtype.add("Wizard");
 
-        this.color.setBlue(true);
         this.power = new MageInt(1);
         this.toughness = new MageInt(1);
 
-        // {tap}, Put the top card of your library into your graveyard: Add {1} to your mana pool.
+        // {T}, Put the top card of your library into your graveyard: Add {1} to your mana pool.
         ColorlessManaAbility ability = new ColorlessManaAbility();
         ability.addCost(new PutTopCardOfYourLibraryToGraveyardCost());
+        ability.setUndoPossible(false);
         this.addAbility(ability);
     }
 

Mage/src/mage/abilities/costs/common/PutTopCardOfYourLibraryToGraveyardCost.java

@@ -33,6 +33,8 @@ import mage.constants.Zone;
 import mage.abilities.Ability;
 import mage.abilities.costs.CostImpl;
 import mage.cards.Card;
+import mage.cards.Cards;
+import mage.cards.CardsImpl;
 import mage.game.Game;
 import mage.players.Player;
 import mage.util.CardUtil;
@@ -65,16 +67,10 @@ public class PutTopCardOfYourLibraryToGraveyardCost extends CostImpl {
     public boolean pay(Ability ability, Game game, UUID sourceId, UUID controllerId, boolean noMana) {
         Player player = game.getPlayer(controllerId);
         if (player != null && player.getLibrary().size() >= numberOfCards) {
-            int i = 0;
             paid = true;
-            while (player.isInGame() && i < numberOfCards) {
-                Card card = player.getLibrary().removeFromTop(game);
-                if (card != null) {
-                    // all cards must reach the graveyard to pay the costs
-                    paid &= card.moveToZone(Zone.GRAVEYARD, sourceId, game, true);
-                }
-                ++i;
-            }
+            Cards cards = new CardsImpl();
+            cards.addAll(player.getLibrary().getTopCards(game, numberOfCards));
+            player.moveCardsToGraveyardWithInfo(cards, ability, game, Zone.LIBRARY);
         }
         return paid;
     }
@@ -82,10 +78,7 @@ public class PutTopCardOfYourLibraryToGraveyardCost extends CostImpl {
     @Override
     public boolean canPay(Ability ability, UUID sourceId, UUID controllerId, Game game) {
         Player player = game.getPlayer(controllerId);
-        if (player != null && player.getLibrary().size() >= numberOfCards) {
-            return true;
-        }
-        return false;
+        return player != null && player.getLibrary().size() >= numberOfCards;
     }
 
     @Override

Mage/src/mage/abilities/mana/ManaAbility.java

@@ -34,6 +34,7 @@ import java.util.UUID;
 import mage.Mana;
 import mage.abilities.ActivatedAbilityImpl;
 import mage.abilities.costs.Cost;
+import mage.abilities.effects.Effect;
 import mage.abilities.effects.common.ManaEffect;
 import mage.constants.AbilityType;
 import mage.constants.Zone;
@@ -46,10 +47,12 @@ import mage.game.Game;
 public abstract class ManaAbility extends ActivatedAbilityImpl {
 
     protected List<Mana> netMana = new ArrayList<>();
-
+    protected boolean undoPossible;
+    
     public ManaAbility(Zone zone, ManaEffect effect, Cost cost) {
         super(AbilityType.MANA, zone);
         this.usesStack = false;
+        this.undoPossible = true;
         if (effect != null) {
             this.addEffect(effect);
         }
@@ -92,4 +95,13 @@ public abstract class ManaAbility extends ActivatedAbilityImpl {
     public boolean definesMana() {
         return netMana.size() > 0;
     }
+
+    public boolean isUndoPossible() {
+        return undoPossible;
+    }
+
+    public void setUndoPossible(boolean undoPossible) {
+        this.undoPossible = undoPossible;
+    }
+    
 }

Mage/src/mage/players/PlayerImpl.java

@@ -1016,7 +1016,7 @@ public abstract class PlayerImpl implements Player, Serializable {
             int bookmark = game.bookmarkState();
             if (ability.activate(game, false)) {
                 if (ability.resolve(game)) {
-                    if (storedBookmark == -1 || storedBookmark > bookmark) { // e.g. usefull for undo Nykthos, Shrine to Nyx
+                    if (ability.isUndoPossible() && storedBookmark == -1 || storedBookmark > bookmark) { // e.g. usefull for undo Nykthos, Shrine to Nyx
                         setStoredBookmark(bookmark);
                     }
                     return true;