The cultist now university student dissatisfied and bored with life, the immortal who spent lifetimes searching for their one and only.

ideals*
Good ending: after that portion of history is successfully carried out, the cultist returns to their time naturally, by the same unknown force. The soldier, distraught, takes the pill left behind and decide to wait and meet the cultists again. Hundreds of years later, they find each other

The soldier has stolen the identity of a dead foreign investigator to take the lead on the cult-cleansjng project, despite it being the most unwanted job.
At first unwavering in their ideas, they make exceptions for the cultist the longer they work together, and feels their strict moral code break

That will transpire. They don't know how to return, but come up with an idea of waiting patiently. They plan on taking the elixir, waiting until they return to their time, then taking the antidote said to have been made to counteract the elixir, making it easier for authorities to handle cultists

against each others' organisations for their own benefit.
Soldier wants greater recognition in the army so that they can have more influence and bring real change
Cultist wants the immortality pill. Actually, the cultist is from the future, sent back by an unknown force, and aware of the events

stay safe moot... 😭