Eos is the last and final boss of the Easy Company Campaign. She will appear after the Bio-Domes in Apollo are clear. On Recruit, her spawn location will be marked on the mini-map. She is a massive creature with several cocoons and egg sacs on her body. Before and during the fight, Charlie Company will assist you with various units, helping to pick away at her health and whittle down her hordes.
During the Black Ops attack, the team usually chooses to defend at the Fort, Scrap Yard, or the hill near the starting zone. While Eos makes her way to the team, Easy Company is fending off waves of undead. The first wave consists of standard Zombies, but later waves will contain Immortals, Hulks, Brood Mothers, Agrons, and Titans.
When Eos approaches, the players may choose to kite or to defend their position. In either case, positioning is vital. Stalkers can still move up cliffs, which is why the hills is slightly less defensible than the fort.
Assault tanks, with Medkits and a Medic's assistance can facetank Eos without taking much damage. Ideally, the tank should be tanking all units, so that dps can focus solely on the boss. Medics should look to save as much energy as possible, using efficient heals such as Nano Weave unless the tank is in danger. Demolitions can also tank Eos with the right armors. When constantly using taunt, a Demo can tank Eos quite well with Reactive Armor, C6, or XS-4 and a Medic to maintain the shield.
At 66% and 33%, Eos will shriek, stunning every unit nearby. She can also frenzy, which allows her to increase her damage output considerably as well as causing her to take increased damage. Whenever she does this, the medic should be on high alert, ready with heals for the damage spike.
Charlie Company will send in reinforcements as the battle drags on. They're fairly ineffective, but they will help if protected.
At 10% health, Eos will flee. Her movespeed increases considerably, requiring stuns and slows so that she does not escape. If she is allowed to escape, you will have to chase her down, while still dealing with the waves of infested. If the fight goes on long enough, Captain Linh will call Broken Arrow. When she announces she will bring in air support, it is time for the players to move. Shortly after the announcement, bombing missions will start. They appear as giant red markers on the ground. (Warning: If you are on a surface such as a bridge, you may not see the dot until it's too late, so beware.) Avoid the bombs and continue to chase her down. She may attack without warning, so only tanks should approach her, even in her low health. Continue to apply stuns and slows, and Eos should go down. Regroup to fight any leftover enemies, and enjoy the victory.
Note that if the battle takes long enough, the air support will stop and fire missions will be called in. These are just like the Forward Observer fire missions. Three strikes are ordered at a time upon Eos. These will slowly bring her health down. However, you shouldn't rely on them to kill her unless her health was already low. Eventually, fire missions will stop and the team will be left alone to fight her. If it gets to this stage, most likely the team didn't have enough firepower to fight her upon first encounter. She will typically retreat to a high ground area and wait. All ambient spawns will stop, and the queen will no longer lay eggs. This makes just finding her exceptionally difficult and dangerous. Be cautions around all ledges and cliffs, for she may be waiting and attack you if you come too close.
When Eos dies she will release a large amount of Parasites. Players should be extremely cautions when dealing the killing blow. Parasites can easily swarm players and kill them outright or stack deadly amounts of venom. Parasites charge on Nightmare making Eos's death even more dangerous.
On higher difficulties, Eos will have a speed buff, making her much faster than normal. Her base speed will increase by 10% to 1.55(+.15).
Only seen in Nightmare Mode, Eos will apply an intimidation debuff on units she attacks. This debuff will lower Health/Shield armor by 1 for 4 seconds. Stacks up to 5 times.
Eos will periodically enter an enraged state, during this period her attack speed and damage is greatly increased, but her armor drops significantly. Eos's attack speed and damage is increased by 30%, rendering Reactive Armor useless against her.
Eos will lay large batches of eggs at intervals as she moves about. These always hatch into Infested Marines on Recruit mode. In Nightmare, eggs will spawn a combination of Stalkers, Infested Marines, and/or cloaked Blindlings. During this period, her movespeed drops down to borderline immobile, and she is quite vulnerable.
The Infested Marines and Stalkers that emerge from Eos’s eggs will have a Rampage buff. They will gain 100% attack speed and 40% movement speed at the expense of 20% reduced attack damage and 90% reduced armor. This will wear off after several seconds. Spawned infested also have Advanced Mutation, giving them 100% increased health.
When heavily injured Eos will let out a terrifying shriek that stuns all allied characters in a 25 radius for slightly under 9 seconds. Even Charlie Company is vulnerable. Before each Shriek, a text will display to warn players, the warning lasting 3.5 seconds before she actually shrieks. The only protection from Shriek is a Demolition's Time To Die or the Medic's Nano Shield. Eos will only shriek twice, at approximately 66 and 33 percent health remaining. Before each Shriek, a text will display to warn players.
Eos is enormous, and as a result can climb over most cliffs and obstructions. Remember this when planning a spot to confront her.
When Eos is mortally wounded, within 10% health left, she will attempt to flee. Her movespeed greatly increases as she tries to avoid the players. Stunlocking her and high damage can put her down before she escapes. If she does flee, she may return at random for one final attack. Once she falls below 8% she will no longer attack players at random. Otherwise the best way to find her is to follow the trail of Infested Marines she breeds, and attack her as she lays more.