Vanishing 12 (This enchantment enters with twelve time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Whenever one or more time counters are removed from this enchantment, scry 1 and you gain 1 life. Then if this enchantment has no time counters on it, exile it. When you do, take an extra turn after this one.
