Two Ur-Dragons is a bit better than one, and this goes completely out of wrack easily with Kolaghan, the Storm's Fury, Old Gnawbone, Terror of the Peaks
Its designed for you to leverage your end step by protecting you from your opponents next big threat but also by letting you use the returned mana to cast something that helps you get ahead
Here are ten staple card draw cards that I often consider when deck building Description : Rhystic Study is an enchantment that allows you to draw a card whenever an opponent casts a spell unless that opponent pays an additional mana
For just 1 blue mana, it counters a noncreature spell unless your opponent pays 2, which is often a back-breaking tempo swing in the early game
That token then gains all of the triggers abilities from all three cards
I'd check them out, and get the high rollers PSA rated ASAP