- Solution attempt #2 for the delayed trigger activator bug: store the original delayed trigger activator and restore it before running the trigger if a stored value was found, in case it was previously overwritten by the AI routines (fixes e.g. Rainbow Vale).

forge-game/src/main/java/forge/game/ability/effects/DelayedTriggerEffect.java

@@ -74,6 +74,7 @@ public class DelayedTriggerEffect extends SpellAbilityEffect {
         if (mapParams.containsKey("Execute")) {
             SpellAbility overridingSA = sa.getAdditonalAbility("Execute");
             overridingSA.setActivatingPlayer(sa.getActivatingPlayer());
+            overridingSA.setDeltrigActivatingPlayer(sa.getActivatingPlayer()); // ensure that the original activator can be restored later
             // Set Transform timestamp when the delayed trigger is created
             if (ApiType.SetState == overridingSA.getApi()) {
                 overridingSA.setSVar("StoredTransform", String.valueOf(sa.getHostCard().getTransformedTimestamp()));

forge-game/src/main/java/forge/game/spellability/SpellAbility.java

@@ -81,6 +81,7 @@ public abstract class SpellAbility extends CardTraitBase implements ISpellAbilit
     private String originalStackDescription = "", stackDescription = "";
     private ManaCost multiKickerManaCost = null;
     private Player activatingPlayer = null;
+    private Player deltrigActivatingPlayer = null; // used by delayed triggers to ensure the original activator can be restored
     private Player targetingPlayer = null;
 
     private boolean basicLandAbility; // granted by basic land type
@@ -374,6 +375,13 @@ public abstract class SpellAbility extends CardTraitBase implements ISpellAbilit
         view.updateCanPlay(this, false);
     }
 
+    public Player getDeltrigActivatingPlayer() {
+        return deltrigActivatingPlayer;
+    }
+    public void setDeltrigActivatingPlayer(final Player player) {
+        deltrigActivatingPlayer = player;
+    }
+
     public Player getTargetingPlayer() {
         return targetingPlayer;
     }

forge-game/src/main/java/forge/game/trigger/TriggerHandler.java

@@ -578,9 +578,15 @@ public class TriggerHandler {
         if (regtrig.getStoredTriggeredObjects() != null) {
             sa.setTriggeringObjects(regtrig.getStoredTriggeredObjects());
         }
+
         if (sa.getActivatingPlayer() == null) { // overriding delayed trigger should have set activator
             sa.setActivatingPlayer(host.getController());
+        } else if (sa.getDeltrigActivatingPlayer() != null) {
+            // make sure that the original delayed trigger activator is restored
+            // (may have been overwritten by the AI simulation routines, e.g. Rainbow Vale)
+            sa.setActivatingPlayer(sa.getDeltrigActivatingPlayer());
         }
+
         if (triggerParams.containsKey("TriggerController")) {
             Player p = AbilityUtils.getDefinedPlayers(regtrig.getHostCard(), triggerParams.get("TriggerController"), sa).get(0);
             sa.setActivatingPlayer(p);