To gain access you have to give Mazarius 30 Demonic Essence. This process was slighting slightly changed on July 31, 2018.
"After a patch released on July 31, 2018 it is no longer possible to start a conversation with Mazarius if you are below level 150. That means it is impossible to gain access to the gates of hell to proceed with the quest if you do not meet the required level."
I would guess your friend either gained access before this change was implemented or got access above level 150 then deleveled the character.
Source: https://tibia.fandom.com/wiki/Ferumbras'_Ascension_Quest