The Elephant Gear from Gradius V

The Shadow Walkers are recurring "bosses" from the Gradius series, always appearing just before the final boss in each game. They are large mechanical contraptions comprised of a tiny body and large legs (the number varying with each model). They serve as the last defense inside the Bacterian fortresses, in order to protect the Bacterian hive minds from invasion. They are indestructible and have no weaponry, using only their massive size and erratic movement as a method of offense. The only option for the player is going through their legs. Few Shadow Walkers can actually be destroyed, like the Elephant Gear, which has various cores on it's legs, though it is very unlikely the player will be able to destroy it.