Bringer of Green Zenith's Twilight

You may pay WUBRG rather than pay this spell's mana cost. If you do, X is 5. Bringer of Green Zenith's Twilight enters the battlefield with X +1/+1 counters on it. If X was 5 or greater, it enters with twice that many counters instead. When Bringer of Green Zenith's Twilight dies, shuffle it into its owner's library.