you mean leveling it? nothing really. Just decreases the re spawn time of your heroes by a very small amount. Don't even bother leveling it unless you want to use it as a decoration since it looks kinda cool at later levels.
It takes away a very short period of time (only a few seconds) per level of your heroes recovery time after falling in battle. It does however create an object with a lot of HP to take care of leaving your attack to damage while not taking damage.