SPOILERS for Agents of S.H.I.E.L.D. episode 'Past Life' ahead
The latest episode of Agents of S.H.I.E.L.D. season 5, 'Past Life', reveals the way to save Earth is to let Phil Coulson (Clark Gregg) die; we break down how and why his death can prevent the planet's destruction. Since the Agents of S.H.I.E.L.D. season 5 premiere, Coulson and his team have been trapped in a future where the Earth was destroyed - supposedly by Daisy Johnson aka Quake (Chloe Bennet) - and the remnants of humanity have been subjugated by Kree. In particular, the humans were ruled over by Kasius (Dominic Rains), a Kree lord who was banished to Earth after angering his father.
Throughout the early part of season 5, Coulson and the team have been looking for a way back to the present, and the Kree Monolith, along with some help from the young Inhuman Flint (Coy Stewart), is their ticket home. Of course, the agents were also searching for a way to save Earth from being destroyed and leading to the future where they've been trapped, but it's still unclear how exactly Agents of S.H.I.E.L.D. will save the world this time. Based on everything we know about how the Earth was destroyed, though it isn't much, S.H.I.E.L.D. is actually responsible for the end of the world.
Related: How Agents of SHIELD Will Get Home
In this week's episode of Agents of S.H.I.E.L.D., 'Past Life', we get new puzzle pieces that offer some insight into the season-long mystery of Earth's destruction. Two particular tidbits of note are Kasius' mention of his father's fixation on Earth and the revelation that S.H.I.E.L.D. will set events into motion that lead to the end of the world when they save Coulson from dying. So, why must Coulson die for the agents to save Earth and how is it connected to Kasius? We break it down and posit a theory for where Agents of S.H.I.E.L.D. season 5 is headed after its hiatus.
Why Does Coulson Have to Die to Save Earth?
Since it was revealed in last week's episode that Kasius has his own seer to even the scales after the precognitive Inhuman Robin helped S.H.I.E.LD. with her visions, fans have wondered who Kasius' seer is. In 'Past Life', Yo-Yo (Natalia Cordova-Buckley) comes across that seer - and the seer turns out to be the future version of Yo-Yo who lived through traveling to the future, returning home, and not being able to stop the Earth from being destroyed. The time travel of Agents of S.H.I.E.L.D. may be confusing, but future Yo-Yo confirms the agents are stuck in a time loop of knowing the Earth will be destroyed, but not knowing how to stop it. Well, future Yo-Yo does give her younger self one way to save Earth: "Phil Coulson is dying, and you have to let him."
Earlier in the episode, Kasius fed some black alien substance he called Odium to the Inhuman trainer Tye (Max E. Williams), whose eyes turned black and shed black tears. Tye attacked Coulson and injured the S.H.I.E.L.D. director, giving him a deadly wound infected with the Odium. While it's unclear what exactly the Odium is or how it will affect Coulson, this is the injury and the illness that Yo-Yo says will kill him. As future Yo-Yo tells her younger self, the Odium infection slowly killing Coulson will force the S.H.I.E.L.D. team to make a choice, either save him and bring about the end of the world or let him die and save the Earth.
Of course, there's a puzzle piece missing here. While we know saving Coulson's life is somehow connected to the destruction of the Earth, we don't know exactly how. Before Yo-Yo can learn as much from her future self, she's urged to leave in order to make it back to her friends. However, insight into Coulson's condition - and how the agents might save him - comes from the other part of the mystery of Earth's destruction that's revealed in 'Past Life'.