“Look out, everybody, things are about to get awesome!”
W4R-D3N is a Constructor miniboss that appears in Borderlands 2. It is the first Constructor fought in the game and thus can tear apart attackers who are not prepared and are unaware of the Constructor's array of deadly attacks. It is found after locating Roland inside of the Bloodshot Stronghold during the main story mission A Dam Fine Rescue. It will grab Roland and begin to take him to the Bloodshot Ramparts, where Hyperion is waiting to take him away.
W4R-D3N has an orange shield which reflects all bullets while it is up, however it does periodically drop. The shield will only drop if an attacker is close enough to W4R-D3N. If they are too far away, it will be permanently engaged, and W4R-D3N will be nearly impossible to destroy.
W4R-D3N's weak spot is the red eye. Players using a sniper rifle will find this an easy target to score a number of guaranteed critical hits during each cycle of shield down-time. In addition, a critical hit while W4R-D3N is constructing another Loader will interrupt the process and the Loader will not spawn.
For maximum effectiveness it is recommended to use a shock weapon to deplete W4R-D3N's shields, then switch to a corrosive weapon once the shields are depleted. Doing this, W4R-D3N can be dispatched with minimal trouble. W4R-D3N'S shields have a very low recharge delay and high recharge rate, so damage over time effects can assist in preventing the shield from coming back up.
It is also worth noting that the Shrine of the Gunbringer behind W4R-D3N makes an excellent hiding spot as the loaders will rarely venture around W4R-D3N and it can only harm players by using a shockwave attack which can easily be avoided by backstepping. From this point, it is remarkably easy to take down W4R-D3N using explosive weaponry such as TORQUE assault rifles as they will tear through W4R-D3N's shields and its armor rather quickly.
W4R-D3N can be defeated during its first appearance at Bloodshot Ramparts, however this is timed. If it is not destroyed in time, it will escape and take Roland to Friendship Gulag.
If it escapes Bloodshot Ramparts, W4R-D3N will be found at the far end of Friendship Gulag. The path to W4R-D3N is full of Loaders, including Badass varieties. Once a path is cleared and the player approaches W4R-D3N, it will start spawning more Loaders, sometimes spawning a Badass version. The Loaders must be dispatched quickly or they will quickly make an already tough boss fight overwhelming.
You can, however, use this to your advantage. If you manage to nearly defeat W4R-D3N within 1-2 minutes at Bloodshot Ramparts with minimal effort, for the sake of extra experience and loot, there is no downside to letting Hyperion take Roland and rescuing him later in the Gulag (killing more enemies and earning more loot in the process). Conversely, if you have had difficulty defeating W4R-D3N before, on a new playthrough you might consider visiting Friendship Gulag as early as possible, then immediately exiting and cramming in several levels before heading to Bloodshot Ramparts. This will level all of the Loaders not spawned directly by W4R-D3N in the Gulag to the level when you first visited there. This way, even if you fail to defeat W4R-D3N at the Ramparts, the following battle in the Gulag will be easier.