Realm of the Underworld

When Realm of the Underworld enters the battlefield, create an 8/8 Legendary creature
token called Cerberus, Father to Hellhounds.
{4}{b}{b}{t}:Exile Realm of the Underworld with 20
time counters on. If Realm of the Underworld
has no time counters on it, transform Realm of
the Underworld.
--I hate this place and I despise everything.
King Osyrus, murderer of sanity