The kaiju terrified people enough that building jaegers wasn't enough, not when the pilots - human, flawed, fragile things - are failing left and right. So they made new kinds of monsters.
Yancy was devastated when Knifehead killed his baby brother after ripping the elder out of the conn-pod. He can still hear Raleigh crying out for the brother that left him alone. He is not eager to jump into action when the Marshall recruits him to train new rangers.
The Shatterdomes learn of the Sentinel Initiative, a program aiming to replacing the Jeagers with smaller versions controlled by A.Is, removing the need for Jeager pilots. None of the Shatterdome workers are happy.
Chuck is particularly pissed then finds to his shock the A.Is are self-aware and constantly alert, something their creators are unaware of. He finds himself visiting them frequently and hiding their lack of shutdown from their scientists.
Then he begins to piece together the true horror of the Sentinel Initiative.
Raleigh Becket is not dead. And he is not alone.
- An Ice Person: Winter is armed with missles loaded with liquid nitrogen
- Awesome Mc Coolname: The Sentinels
- Badass in Distress: The Sentinels are giant mechas and at least one is a former Jaegar pilot. And they're at the mercy of Lopez's team, which prompts Herc to insist they move slowly in regards to their scheme to expose Lopez's team.
- Benevolent A.I.: The Sentinel A.Is fight Kajui to protect humanity and are very sweet to Chuck. Of course, it is clear that they are not actually A.Is.
- Big Little Brother: Raleigh is a variation of this. His sentinel body is much larger than Yancy. However, neither of them are aware of this as Yancy believes his brother dead and Raleigh had his memories wiped. It is also possible that Raleighs actual body is intact as it hasnt been stated exactly how the people get into the sentinels.
- Despair Event Horizon: The fight against Knifehead and Raleigh's supposed fate was this to Yancy.
- Driven to Suicide: Yancy. He was saved.
- Hell Is That Noise: When Chuck mentions to the Sentinels that the team that built them is returning, they are...distressed.
- Identity Amnesia: The Sentinels. Justified as their memories were regularly wiped on purpose by the scientists. There's a reason they avoid alerting them to the fact they're self-aware.
- "It" Is Dehumanizing: Averted. Chuck initial refers to Steel as it but quickly switches to using gender pronouns for the sentinels.
- Just a Machine: The sentinels weird out some of the Shatterdome staff because they are this. However, Chuck and later Mako soon find they are more.
- Man in the Machine: All of the Sentinels are this.
- My Greatest Failure: Raleighs death is this to Yancy.
- Psychic Link / Mental Fusion: The Sentinels share these with each other as they are constantly drifting with each other. When they inform Chuck of this, it alerts him to the fact that they were not as Lopez and his team claimed. There are also indications of this between Yancy and Raleigh/Steel.
- Shock and Awe: Steel is armed with electrified lances
- Sibling Yin-Yang: Played with. At the beginning, Yancy is described as calm and level-headed with Raleigh more energetic and affection, with the public seeing Raleigh as the heart and Yancy as the head. However, it is stated that in Gipsy Danger, they are one unit and therefore both. Then Knifehead happens.
- Survivor Guilt: Yancy lived when Raleigh (as far as he knows) died. He hates himself for it.
- We Have Reserves: Word of God says that it took a lot of tries to get a Sentinel working and a lot of test subjects died in the process. The scientists had this attitude towards the number of people they were killing.