Warden is located at the end of The Anvil district on the planet Eden-6.
You can farm Warden for these legendary weapons as it is the dedicated loot source for these items. Warden has a 30% legendary drop chance.
Warden is a Goliath and therefore will be able to enrage and level up. His first life bar is an armor bar. Every time Warden loses a third of this yellow armor bar, he will become temporarily invulnerable.
Warden will shoot rockets and lasers during his Armor phase. If you keep your distance and strafe in circles around Warden, you should be fine.
During Warden’s Red Health Bar phase, he will enrage and start jumping around and attack you with melee attacks. Watch out because he’s able to leap great distances.
When his health drops below 1/3, he will attempt to kill nearby friendly units. This will level up him up, which will make him stronger and his health bar will be restored. While he is vulnerable during the transformation he can eventually level up 5 times and reach the Godly state.