Whether or not you choose to use the Dragon's Call item, the selected dragon will assault your team as you play the level.
It's more of a key than a weapon, as you don't equip or attack enemies with it.
You can even climb ladders, visiting the same location from above and below.
The level does have a random element of sorts, though: dragons!
None of Inquisition's multiplayer characters can be purchased outright, so you will have to craft whichever heroes you're interested in but don't have yet.
The way Inquisition multiplayer's loot system works is: as you play levels, you'll occasionally find new items as loot, but they're uncommon.