Alternative cost - fixed that it doesn't allow to cast cards that was affected by cost modification effects (example: Prowl ability, see #6698);

Mage/src/main/java/mage/abilities/condition/common/ProwlCostWasPaidCondition.java

@@ -0,0 +1,38 @@
+package mage.abilities.condition.common;
+
+import mage.abilities.Ability;
+import mage.abilities.condition.Condition;
+import mage.abilities.keyword.ProwlAbility;
+import mage.cards.Card;
+import mage.game.Game;
+
+/**
+ * Checks if a the spell was cast with the alternate prowl costs
+ *
+ * @author LevelX2
+ */
+public enum ProwlCostWasPaidCondition implements Condition {
+
+    instance;
+
+    @Override
+    public boolean apply(Game game, Ability source) {
+        Card card = game.getCard(source.getSourceId());
+        if (card != null) {
+            for (Ability ability : card.getAbilities()) {
+                if (ability instanceof ProwlAbility) {
+                    if (((ProwlAbility) ability).isActivated(source, game)) {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return "{source}'s prowl cost was paid";
+    }
+
+}