Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
Sacred elixir ushers in doom
S13E19
·
The Brain of Morbius Part 3
To
Doctor challenges Sisterhood over Elixir
S13E19
·
The Brain of Morbius Part 3
Why These Connect
The narrative assertion
"The Sisterhood's critical shortage of the Elixir of Life directly motivates the Doctor's attempt to obtain it for Sarah's blindness, setting up the core conflict with the Sisterhood and their initial antagonism toward the Doctor."
About Causal Connections
A directly causes B. The first event sets forces in motion that produce the second. These are the load-bearing connections of plot--remove one and the story structure collapses.