When Mogg Fanatic dies, Mortuary and Funeral Room // Awakening Hall trigger.
Resolve the Mortuary trigger, putting Mogg Fanatic from your graveyard onto the top of your library.
Resolve the Funeral Room // Awakening Hall trigger, causing you to gain 1 life and each opponent to lose 1 life.
Resolve the Mogg Fanatic ability.
Cast Mogg Fanatic from the top of your library by paying 1 life.
Repeat.
This loop turns a humble goblin into an endless cycle of doom, fueled entirely by the dark power of Bolas's Citadel allowing you to bypass mana costs and play straight from the top of your library for a mere pittance of life. Whenever Mogg Fanatic sacrifices itself to ping a target, Mortuary immediately intercepts it on its way to the graveyard to place it right back on top of your library where the Citadel can grab it again. Meanwhile, the Awakening Hall half of Funeral Room // Awakening Hall catches every single death trigger to continuously drain your opponents and pad your life total, ensuring you never run out of life to pay for your recurring spells.