[SOLVED] Using /fill command to "open" a doorway ~onDeath

Trying to create a mob that will "/fill" a wall with air to open up passage once a player has killed the mob.

I believe I'm having an issue with the /fill command not knowing what world to activate in, so it's not functioning properly.

I've tried adding in the @self target to see if that would help but it still doesn't work. I've also tried using the example in the manual and adding...

[SOLVED] Using /fill command to "open" a doorway ~onDeath