A BrainExplode

A_BrainExplode is a code pointer used in the death animation for the Big Brain.

spawns a rocket explosion effect near the thing that triggered the function, and sets the state of that thing to  (frame #799). Since this is followed after two frames by  which again calls , the result is a continually exploding wall effect that completes until the boss brain object calls   that triggers the level exit.

Uses
The  code pointer appears in the following states in Doom's state table:

Example
The following is an example of how to set the  code pointer in a Dehacked file:

Pointer 21 (Frame 34) Codep Frame = 801

Or using BEX syntax:

[CODEPTR] Frame 1234 = BrainExplode