EOS circles the combat arena from a great distance, rendering beam lasers completely ineffective. EOS also has massive health and shield pools, approaching the levels generally reserved for raid bosses. Its offensive capability is extreme as well, and can easily send Vault Hunters into Fight For Your Life very quickly. During the battle, bugs and glitches will constantly spawn, and are often best left alone until needed to provide a Second Wind.
EOS has a number of main attacks:
- Moonshot Cannon: This attack will fire a number of projectiles streaming at the Vault Hunters
- Eye Laser: The Eye Laser is EOS's most devastating attack, and can almost immediately down any Vault Hunter who takes the full brunt of it. The firing of this laser does present a lucrative opportunity to the Vault Hunters, though - from the time EOS's Eye starts opening to prepare for the strike, until it closes shortly after finishing the attack, the Eye is EOS's single critical hit area, so Vault Hunters are encouraged to attack that area when given the opportunity.
In addition to its larger attacks, EOS has multiple turrets attached to it. These start out by firing ion blasts at the Vault Hunters but later start firing homing missiles as well. The turrets are vulnerable to corrosive damage, but like EOS they have a massive health pool, and Vault Hunters might not find it worth it to take the time to destroy them.
Once EOS's shields are finally depleted and it takes actual health damage, EOS will eventually disappear from the arena for awhile to recharge its shields back to full. This will generally happen at least twice during the battle. While charging, EOS will generate large holographic images of Lilith and other allies, attempting to discourage and demoralize the Vault Hunters. These images do not otherwise interact with the battle, and can be ignored.
Also during the shield-recharge periods, harder versions of bugs and glitches will start spawning, including Badass Glitches which have reflective shields which can quickly down a Vault Hunter if fired into. During the final round of battle with EOS, these heavier mobs will continue to spawn to further antagonize the Vault Hunters, in addition to EOS stepping up its aggressiveness. The Badass enemies spawned during the final stages will often need to be addressed, rather than letting them be.
Once EOS is finally defeated, 5H4D0W-TP will appear on its throne, lying on its back, the H-Source ready to be plucked out. 5H4D0W-TP will blow a raspberry and generate a large pool of good loot, including Moonstone, glitch and purple items. After the main bulk of the loot has dropped, a final legendary item is guaranteed to spawn, accompanied by another raspberry sound.
- Main article: System Shutdown
- EOS can often take a very long time to destroy. Certain equipment combinations are capable of generating enough damage to take out EOS very quickly if deployed properly, but Vault Hunters approaching the battle without extensive gear preparation ahead of time should expect to spend at least tens of minutes fighting the battle, and many people end up spending an hour or more on this battle alone.
- Fighting EOS in co-op mode should be easier than attempting it solo, since EOS's attacks would be split between the Vault Hunters. This is especially useful if a Vault Hunter is caught by the Eye Laser attack, since even if one Vault Hunter dies, the other(s) will remain in the fight, so EOS won't regenerate health or shields.
- If EOS receives enough damage at once, its shield-recharge phases can be skipped, but this is basically impossible to do without either using a very over-levelled Vault Hunter (with matching over-levelled gear), or by exploiting glitches/bugs to increase the Vault Hunter's damage output well over intended levels.
- When fighting EOS outside of the story missions, it's possible to not receive the legendary drop. If the Vault Hunters are far enough away from 5H4D0W-TP's resting place (near the entrance to the level), the sound effects which accompany the loot drops will play, but the main barrage of loot does not actually spawn until the Vault Hunters get close enough. If the Vault Hunters are not within item-spawning range during the second raspberry (which signals the legendary drop), that item will not spawn at all.