Use generics to ensure the correct class types stored inside the costs tags.

Mage/src/main/java/mage/abilities/Ability.java

@@ -170,13 +170,6 @@ public interface Ability extends Controllable, Serializable {
      * Set tag to the value, initializes this ability's tags map if it is null
      */
     void setCostsTag(String tag, Object value);
-    /**
-     * Returns the value of the tag or defaultValue if the tag is not found in this ability's tag map
-     * does NOT check the source permanent's tags, use CardUtil.getSourceCostsTag for that
-     *
-     * @return The given tag value (or the default if not found)
-     */
-    Object getCostsTagOrDefault(String tag, Object defaultValue);
 
     /**
      * Retrieves the effects that are put into the place by the resolution of