- Some crash prevention in ChangeTargetsAi, the AI needs further improvement here if we're to teach it to retarget spells with multiple targets.

- Generalized ChangeTargetsAi not to mention Spellskite by name (so other creatures can gain its ability and be correctly used by the AI) and also not to use AI Logic and detect the ability via DefinedMagnet instead.
- Marking Muck Drubb as AI playable.

forge-ai/src/main/java/forge/ai/ability/ChangeTargetsAi.java

@@ -6,6 +6,7 @@ import forge.ai.ComputerUtilMana;
 import forge.ai.SpellAbilityAi;
 import forge.card.mana.ManaCost;
 import forge.card.mana.ManaCostParser;
+import forge.card.mana.ManaCostShard;
 import forge.game.Game;
 import forge.game.mana.ManaCostBeingPaid;
 import forge.game.player.Player;
@@ -26,11 +27,9 @@ public class ChangeTargetsAi extends SpellAbilityAi {
         final Game game = sa.getHostCard().getGame();
         final SpellAbility topSa = game.getStack().isEmpty() ? null : ComputerUtilAbility.getTopSpellAbilityOnStack(game, sa);
 
-        if (sa.hasParam("AILogic")) {
+        if ("Self".equals(sa.getParam("DefinedMagnet"))) {
-            if ("SpellMagnet".equals(sa.getParam("AILogic"))) {
             return doSpellMagnet(sa, topSa, aiPlayer);
         }
-        }
 
         // The AI can't otherwise play this ability, but should at least not miss mandatory activations (e.g. triggers).
         return sa.isMandatory();
@@ -41,11 +40,9 @@ public class ChangeTargetsAi extends SpellAbilityAi {
         final Game game = sa.getHostCard().getGame();
         final SpellAbility topSa = game.getStack().isEmpty() ? null : ComputerUtilAbility.getTopSpellAbilityOnStack(game, sa);
 
-        if (sa.hasParam("AILogic")) {
+        if ("Self".equals(sa.getParam("DefinedMagnet"))) {
-            if ("SpellMagnet".equals(sa.getParam("AILogic"))) {
             return doSpellMagnet(sa, topSa, aiPlayer);
         }
-        }
 
         return true;
     }
@@ -64,8 +61,18 @@ public class ChangeTargetsAi extends SpellAbilityAi {
 
         if (!topSa.usesTargeting() || topSa.getTargets().getTargetCards().contains(sa.getHostCard())) {
             // if this does not target at all or already targets host, no need to redirect it again
+
+            // TODO: currently the AI does not know how to change several targets to the same object (e.g.
+            // Cone Flame) and will stupidly keep retargeting the first available target unless stopped here.
+            // Needs investigation and improvement.
             return false;
         }
+        if (topSa.getTargets().getNumTargeted() > 1 && topSa.hasParam("DividedAsYouChoose")) {
+            // TODO: currently the AI will crash the game if it tries to change the target of a SA with a
+            // divided allocation map. May need improvement.
+            return false;
+        }
+
         if (topSa.getHostCard() != null && !topSa.getHostCard().getController().isOpponentOf(aiPlayer)) {
             // make sure not to redirect our own abilities
             return false;
@@ -75,7 +82,8 @@ public class ChangeTargetsAi extends SpellAbilityAi {
             return false;
         }
         
-        if ("Spellskite".equals(sa.getHostCard().getName())) {
+        if (sa.getPayCosts().getCostMana() != null && "{P/U}".equals(sa.getPayCosts().getCostMana().getMana().getShortString())) {
+            // e.g. Spellskite or a creature receiving its ability that requires Phyrexian mana P/U
             int potentialDmg = ComputerUtil.predictDamageFromSpell(topSa, aiPlayer);
             boolean canPayBlue = ComputerUtilMana.canPayManaCost(new ManaCostBeingPaid(new ManaCost(new ManaCostParser("U"))), sa, aiPlayer);
             if (potentialDmg != -1 && potentialDmg <= 2 && !canPayBlue && topSa.getTargets().getTargets().contains(aiPlayer)) {

forge-gui/res/cardsfolder/m/mizzium_meddler.txt

@@ -4,6 +4,6 @@ Types:Creature Vedalken Wizard
 PT:1/4
 K:Flash
 T:Mode$ ChangesZone | Origin$ Any | Destination$ Battlefield | ValidCard$ Card.Self | Execute$ TrigChange | OptionalDecider$ You | TriggerDescription$ When CARDNAME enters the battlefield, you may change a target of target spell or ability to CARDNAME.
-SVar:TrigChange:AB$ ChangeTargets | Cost$ 0 | TargetType$ Spell,Activated,Triggered | ValidTgts$ Card | DefinedMagnet$ Self | ChangeSingleTarget$ True | AILogic$ SpellMagnet
+SVar:TrigChange:AB$ ChangeTargets | Cost$ 0 | TargetType$ Spell,Activated,Triggered | ValidTgts$ Card | DefinedMagnet$ Self | ChangeSingleTarget$ True
 SVar:Picture:http://www.wizards.com/global/images/magic/general/mizzium_meddler.jpg
 Oracle:Flash (You may cast this spell any time you could cast an instant.)\nWhen Mizzium Meddler enters the battlefield, you may change a target of target spell or ability to Mizzium Meddler.

forge-gui/res/cardsfolder/m/muck_drubb.txt

@@ -6,6 +6,5 @@ K:Flash
 T:Mode$ ChangesZone | Origin$ Any | Destination$ Battlefield | ValidCard$ Card.Self | Execute$ TrigChange | TriggerDescription$ When CARDNAME enters the battlefield, change the target of target spell that targets only a single creature to Muck Drubb.
 SVar:TrigChange:AB$ ChangeTargets | Cost$ 0 | TargetType$ Spell | ValidTgts$ Card | DefinedMagnet$ Self | TargetsSingleTarget$ True | TargetValidTargeting$ Creature
 K:Madness:2 B
-SVar:RemAIDeck:True
 SVar:Picture:http://www.wizards.com/global/images/magic/general/muck_drubb.jpg
 Oracle:Flash (You may cast this spell any time you could cast an instant.)\nWhen Muck Drubb enters the battlefield, change the target of target spell that targets only a single creature to Muck Drubb.\nMadness {2}{B} (If you discard this card, you may cast it for its madness cost instead of putting it into your graveyard.)

forge-gui/res/cardsfolder/s/spellskite.txt

@@ -2,6 +2,6 @@ Name:Spellskite
 ManaCost:2
 Types:Artifact Creature Horror
 PT:0/4
-A:AB$ ChangeTargets | Cost$ PU | TargetType$ Spell,Activated,Triggered | ValidTgts$ Card | DefinedMagnet$ Self | ChangeSingleTarget$ True | AILogic$ SpellMagnet | SpellDescription$ Change a target of target spell or ability to CARDNAME.
+A:AB$ ChangeTargets | Cost$ PU | TargetType$ Spell,Activated,Triggered | ValidTgts$ Card | DefinedMagnet$ Self | ChangeSingleTarget$ True | SpellDescription$ Change a target of target spell or ability to CARDNAME.
 SVar:Picture:http://www.wizards.com/global/images/magic/general/spellskite.jpg
 Oracle:{P/U}: Change a target of target spell or ability to Spellskite. ({P/U} can be paid with either {U} or 2 life.)