a little off topic but........

no. you need the phrase to open the door to the sactuary.

your character will not know it if you don't meet Astrid.

Thanks, I wasn't trying to steal the OP's thread. Since his question was already answered, I tacked mine on.

Only if you take the opposite route of destroying the Dark Brotherhood. Join them or destroy them, those are the only two options to gain access to the Sanctuary and thus the Word Wall for Marked for Death.