When a card that allows "free cast" is in play, do not prefer to discard "unplayable" cards based on CMS, instead discard worst as normal.

...but AI still isn't very eager to actually play them for some reason.

forge-ai/src/main/java/forge/ai/AiController.java

@@ -1046,8 +1046,22 @@ public class AiController {
                     numLandsAvailable++;
                 }
 
-                //Discard unplayable card
+                // Discard unplayable card
                 boolean discardedUnplayable = false;
+                // But check if there is a card in play that allows casting spells for free!
+                // if yes, nothing is unplayable, at least based on CMC
+                boolean dreamHalls = false;
+                for (Card cardInPlay : game.getCardsIn(ZoneType.Battlefield)) {
+                    if (cardInPlay.hasSVar("AllowFreeCast")) {
+                        if ("Everyone".equals((cardInPlay.getSVar("AllowFreeCast")))) {
+                            dreamHalls = true;
+                        } else if (("Owner".equals((cardInPlay.getSVar("AllowFreeCast"))))
+                                && (cardInPlay.getOwner().equals(player))) {
+                            dreamHalls = true;
+                        }
+                    }
+                }
+                if (!dreamHalls) {
                     for (int j = 0; j < validCards.size(); j++) {
                         if (validCards.get(j).getCMC() > numLandsAvailable && !validCards.get(j).hasSVar("DoNotDiscardIfAble")) {
                             discardList.add(validCards.get(j));
@@ -1059,6 +1073,7 @@ public class AiController {
                             break;
                         }
                     }
+                }
 
                 if (!discardedUnplayable) {
                     // discard worst card

forge-ai/src/main/java/forge/ai/AiCostDecision.java

@@ -65,6 +65,20 @@ public class AiCostDecision extends CostDecisionMakerBase {
         final String type = cost.getType();
         CardCollectionView hand = player.getCardsIn(ZoneType.Hand);
 
+/*        // Dream Halls
+        if (type.equals("Card.SharesColorWith")) {
+        Card bestfound= null;
+        for (Card card : hand) {
+            if ((card.sharesColorWith(source))
+                && (!card.equals(source))) {
+            if (bestfound==null) { bestfound=card; }
+            if (card.getCMC()<bestfound.getCMC())  { bestfound=card; }
+            }
+        }
+        if (bestfound==null) { return null; } else
+        { return PaymentDecision.card(bestfound); }
+        } else */
+
         if (type.equals("LastDrawn")) {
             if (!hand.contains(player.getLastDrawnCard())) {
                 return null;

forge-gui/res/cardsfolder/d/dream_halls.txt

@@ -4,5 +4,6 @@ Types:Enchantment
 S:Mode$ Continuous | Affected$ Card.nonToken | AddKeyword$ Alternative Cost:Discard<1/Card.SharesColorWith/color sharing> | AffectedZone$ Hand,Graveyard,Exile,Library,Command | Description$ Rather than pay the mana cost for a spell, its controller may discard a card that shares a color with that spell.
 SVar:NonStackingEffect:True
 AI:RemoveDeck:Random
+SVar:AllowFreeCast:Everyone
 SVar:Picture:http://www.wizards.com/global/images/magic/general/dream_halls.jpg
 Oracle:Rather than pay the mana cost for a spell, its controller may discard a card that shares a color with that spell.

forge-gui/res/cardsfolder/o/omniscience.txt

@@ -2,6 +2,7 @@ Name:Omniscience
 ManaCost:7 U U U
 Types:Enchantment
 S:Mode$ Continuous | Affected$ Card.nonLand+YouOwn | MayPlay$ True | MayPlayWithoutManaCost$ True | AffectedZone$ Hand | Description$ You may cast spells from your hand without paying their mana costs.
+SVar:AllowFreeCast:Owner
 AI:RemoveDeck:Random
 SVar:Picture:http://www.wizards.com/global/images/magic/general/omniscience.jpg
 Oracle:You may cast spells from your hand without paying their mana costs.