"Escape to Salvation" - "Magnificent Retreat" [Campaign 4, Mission 4]

To replace the heroes' development, you need to complete the last mission in which they are involved, from beginning to end. If everything is clear with Wolfenstein and Frida, then for Kujin, you need to specifically complete the fourth mission of the Orcish campaign. But in these battles, the heroes' development (except for Zehir, of course) does not play a significant role.