In Adventurers, your end goal is to kill all the other players. First, though, you must toughen yourself up by killing computer units and levelling up. The level up system is quite interesting: When you level up, you get gold. Spread across the map there are musketeer booths. At the musketeer booths you can spend your gold on speed, attack, or defense upgrades. (The upgrade you are getting is the name of the musketeer.)
You start the game with a surgeon. However, should your surgeon die, you can get another one at healer stations spread across the map. At healer stations you get a 1-hp healer.
(There is a bug with healer stations where you get ~5-6 healers. I do not know how to fix this.)