Quirion Ranger, Ignoble Hierarch, Imperial Recruiter, and the evoke creatures add significant gains to archetypes like these
These all give you access to powerful removal, counterspell, and protection, something very much appreciated in a deck like Calvary Charge that wants a lot of creatures on the battlefield on your side and little on your opponents'
Mana Crypt adds to generic mana to your mana pool which is amazing for a zero mana artifact, with just the small downside of a 50/50 chance of taking 3 damage at the start of your turn
You also get counters on all of your existing creatures, which can be a big swing
One common trade is life for cards
After that, he hangs around - something Fireball doesn't do