Hey guise. Mind if I pick your brains?

Ok so I always structure each of my projects in a 3 Act structure, with each act punctuated by a major event, usually some disaster for the characters to deal with. The first disaster comes at the end of Act 1. The second disaster is the mid-point of Act 2, and the third disaster is the end of Act 2; and forces Act 3 which wraps things up. I like to have the first disaster be caused by external circumstances, but the second and third disasters caused by my protag’s attempts to “fix things”. Things just get worse and worse

So this is my first horror project and im having trouble coming up with disaster number 3. My protags enter a supposedly haunted crypt in search of a Mcguffin. They get sealed in (D1) and must escape the entity sealed inside with them. The party consists of 6 and D2 comes when the most capable of them "the man with the plan" dies. I cant figure out what happens after. I dont have my D3 or my Act 3 and its been about a week of halted progress because of it. Im stumped and so Ive been picking the brains of those around me. Thought Id ask a forum of fellow writers too. All genres follow a formula, but i really just cant pinpoint a 3rd disaster, that ultimately forces my Act 3, which is likely a final confrontation and escape. I thought about making D2 in to D3 but I really wanna drive home the hopelessness when the man with the plan dies. I want him to die earlier than not to really decrease my parties chance of survival.

You guys have any thoughts, ideas or insights?