It is a very odd mana rock, because you are spending mana to get 1 less than you spent, but I think the threat here is that it then also becomes an 8/8 that makes opponents start sacrificing permanents, which seems pretty strong, especially since it is safe from creature-based removal until you turn it on
If you do win this battle, youll be able to get a pretty cool dinosaur
Whenever you attack, you may mill a card
Haven of the Spirit Dragon works for any color dragon deck, and Cinder Glade benefits from having basic land types to work in conjunction with Game Trail
And it looks 'good', right
I prefer to kill them, but even if youre just playing a spell for the untap trigger you can go off with Aetherflux Reservoir