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.
Near Mint - $99.80
Lightly Played - $89.80
Played - $69.90
Heavily Played - $59.90
Damaged - $49.90
Near Mint Non-English - $99.80
Lightly Played Non-English - $89.80
Played Non-English - $69.90
Heavily Played Non-English - $59.90
Damaged Non-English - $49.90