Fix text-changing Possessed Aven.

forge-game/src/main/java/forge/game/CardTraitBase.java

@@ -43,6 +43,9 @@ public abstract class CardTraitBase extends GameObject {
     /** Keys of descriptive (text) parameters. */
     private static final ImmutableList<String> descriptiveKeys = ImmutableList.<String>builder()
             .add("Description", "SpellDescription", "StackDescription", "TriggerDescription").build();
+    /** Keys to be followed as SVar names when changing text. */
+    private static final ImmutableList<String> mutableKeys = ImmutableList.<String>builder()
+            .add("AddAbility").build();
 
     /**
      * Sets the temporary.
@@ -357,15 +360,19 @@ public abstract class CardTraitBase extends GameObject {
     public void changeText() {
         for (final String key : this.mapParams.keySet()) {
             final String value = this.originalMapParams.get(key), newValue;
-            // change descriptions differently
             if (descriptiveKeys.contains(key)) {
+                // change descriptions differently
                 newValue = AbilityUtils.applyDescriptionTextChangeEffects(value, this);
-            }
+            } else if (mutableKeys.contains(key)) {
-            // don't change literal SVar names!
+                // follow SVar and change it
-            else if (!this.getHostCard().hasSVar(key)) {
+                final String originalSVarValue = hostCard.getSVar(value);
-                newValue = AbilityUtils.applyAbilityTextChangeEffects(value, this);
+                hostCard.changeSVar(value, AbilityUtils.applyAbilityTextChangeEffects(originalSVarValue, this));
-            } else {
                 newValue = null;
+            } else if (this.getHostCard().hasSVar(value)) {
+                // don't change literal SVar names!
+                newValue = null;
+            } else {
+                newValue = AbilityUtils.applyAbilityTextChangeEffects(value, this);
             }
 
             if (newValue != null) {

forge-game/src/main/java/forge/game/card/Card.java

@@ -22,6 +22,7 @@ import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
 import com.google.common.collect.Sets;
 
 import forge.GameCommand;
@@ -123,6 +124,8 @@ public class Card extends GameEntity implements Comparable<Card> {
     private final CardChangedWords changedTextTypes = new CardChangedWords();
     /** List of the keywords that have been added by text changes. */
     private final List<String> keywordsGrantedByTextChanges = Lists.newArrayList();
+    /** Original values of SVars changed by text changes. */
+    private Map<String, String> originalSVars = Maps.newHashMap();
 
     private final ArrayList<Object> rememberedObjects = new ArrayList<Object>();
     private final MapOfLists<GameEntity, Object> rememberMap = new HashMapOfLists<GameEntity, Object>(CollectionSuppliers.<Object>arrayLists());
@@ -4609,6 +4612,7 @@ public class Card extends GameEntity implements Comparable<Card> {
      * Update the changed text of the intrinsic spell abilities and keywords.
      */
     private final void updateChangedText() {
+        resetChangedSVars();
         final List<CardTraitBase> allAbs = ImmutableList.<CardTraitBase>builder()
             .addAll(this.getSpellAbilities())
             .addAll(this.getStaticAbilities())
@@ -4640,6 +4644,26 @@ public class Card extends GameEntity implements Comparable<Card> {
         this.changedTextTypes.copyFrom(other.changedTextTypes);
     }
 
+    /**
+     * Change a SVar due to a text change effect. Change is volatile and will be
+     * reverted upon refreshing text changes (unless it is changed again at that
+     * time).
+     * 
+     * @param key the SVar name.
+     * @param value the new SVar value.
+     */
+    public final void changeSVar(final String key, final String value) {
+        originalSVars.put(key, getSVar(key));
+        this.setSVar(key, value);
+    }
+
+    private void resetChangedSVars() {
+        for (final Entry<String, String> svar : originalSVars.entrySet()) {
+            this.setSVar(svar.getKey(), svar.getValue());
+        }
+        originalSVars.clear();
+    }
+
     /**
      * <p>
      * getIntrinsicAbilities.