With Crush Arrow dealing massive damage while stripping Energy from the Active Pokmon, Decidueye ex excels at shutting down opposing attackers
They can also pair well with your removal spells if you have spells like Reanimate
[casthaven]Padeem, Consul of Innovation[/casthaven] [casthaven]Arcum Dagsson[/casthaven], [casthaven]Memnarch[/casthaven], and [casthaven]Muzzio, Visionary Architect[/casthaven] have another friend to potentially lead their artificial armies against the forces of nature upon which monoblue decks so commonly choke
You can only use each effect of "Ancient Gear Commander" once per turn
There are plenty of Two-Energy attackers (Iron Valiant, Klawf) that will significantly benefit from having this card around.
On your turn, you can play a land and cast a spell from the cards milled that turn, allowing you to utilize resources from any graveyard