Joseph Joestar arrives at the base to rescue Speedwagon. When Santana escapes his cell and begins slaughtering the soldiers, Joseph intervenes. Initially, Joseph tries to "make friends" with the creature to gauge its intelligence, but he quickly realizes Santana is a predator who views humans as mere food.
Joseph and Josuke find an "invisible baby" (Shizuka Joestar). JoJo`s Bizarre Adventure Episode 13
The battle moves toward the surface as Joseph tries to expose Santana to direct sunlight. Joseph Joestar arrives at the base to rescue Speedwagon
The final battle against DIO, where Jotaro and DIO have their climactic showdown in Cairo. Joseph and Josuke find an "invisible baby" (Shizuka Joestar)
The fight against Santana described above.
Depending on which version of JoJo you are watching, "Episode 13" refers to different storylines:
Joseph allows himself to be "eaten" by Santana. Once inside the creature's body, Joseph releases a massive burst of Hamon from the inside, where Santana has no protection. Stroheim’s Sacrifice