I'd consider cutting Answered Prayers if its in here for the lifegain. The additional effect of Answered Prayers, of becoming an angel, I think is negligible. Maybe consider Daxos, Blessed by the Sun, which continues the lifegain theme, is less mana and is another body to trigger other similar effects. Daxos additionally gives you a decent blocker if needed. While he is a little more easy to remove given two typings, you do have multiple enchantment recur effects to consider it.

You got a couple of Snow-Lands, so maybe consider, On Thin Ice, its removal, and can be recurred here if removed.

While Mana Vault, and Mana Crypt allow for fast mana plus the bonus of self-inflicting damage for Darien, Basalt Monolith seems a little less helpful here. It does provide fast mana, but only once and then it usually sits there until you have the resources to untap it. I'd consider Extraplanar Lens it comes the same turn and provides asymmetrical ramp for you (unless your meta runs a lot of snow plains?). Even if Extraplanar isn't your preference, I still would prefer to fit other ramp in here besides Basalt, which usually shines in decks that can untap it to abuse of it more.

That said it seems like a great deck, I've seen a my fair share of Darien decks, and this seems like one of the more consistent and fun ones to play.