0 mana DIE INSECT! Majordomo Reno Priest

The one goal of this deck.

Guide

Removal Package - Helps you survive to the Majordomo turn

Spirit Lash

Shadow Word: Death or Shadow Word: Ruin

Mass Hysteria

Lightbomb

Psychic Scream

Plague of Death

This deck has a lot of removal that is useful to survive until you can play your Majordomo turn, but remember to save either Shadow Word: Death or Shadow Word: Ruin for the Majordomo package

Highlander Package - Helps with survival, card draw, and making your Ragnaros hero power cost zero

Kazakus - Can be used for removal or card draw, card draw is usually better if you have a lot of removal in your hand because you are trying to draw to your Majordomo package as fast as possible and you have Archbishop Benedictus to prevent fatigue so if you draw fast and have few cards you will have plenty of time to use your hero power as Ragnaros 

Raza the Chained - The zero mana hero power can help you heal each turn, and when you are Ragnaros your hero power will also cost zero

Zephrys the Great - Extra removal or can be played for tempo

Reno Jackson - Heals you up, very useful

Deathrattle Package - Get Amara, Warden of Hope to use for your Majordomo turn

Awaken the Makers - the quest, gets you an Amara, Warden of Hope

Crystalline Oracle - cheap card for getting a deathrattle tick, the extra value from the card you get can be useful

Dead Ringer - completes a tick of the quest and draws you another deathrattle card

Twilight's Call - completes two ticks of the quest at once

Mistress of Mixtures - heals you and helps against burn and aggro

Bloodmage Thalnos - draws you a card and synergy with Spirit Lash

Loot Hoarder - draws you a card

There is enough card draw and enough deathrattle minions (that are low cost and can be played early on) in this deck to complete the quest relatively quickly

Majordomo Package - Become a 40 health Ragnaros, the Firelord

Shadow Word: Death or Shadow Word: Ruin - You need to save one of these for Majordomo, use the other for removal

Gilded Gargoyle

Maiev Shadowsong

Emperor Thaurissan

Majordomo Executus

First, you need a coin from Gilded Gargoyle.  Then, play Emperor Thaurissan when you have Maiev Shadowsong and Majordomo Executus in hand.  Finally, play Majordomo Executus and use Maiev Shadowsong on him in the same turn and in 2 turns use either Shadow Word: Death or Shadow Word: Ruin and play Amara, Warden of Hope which you should have from the Awaken the Makers quest.  You will now be Ragnaros, the Firelord and have 40 health.  You can play Raza the Chained before or after the Majordomo turn and you will also have a zero mana DIE INSECT! hero power.  From there, have fun with Ragnaros's emotes and blasting fire at your opponent and their minions.

Support Package - Cards that support the gameplan and help get more use out of the other packages

Raise Dead - You can get 2 more deathrattles for your quest or useful Highlander cards

Seance - You can use it to copy an extra deathrattle or Highlander card, or play Amara, Warden of Hope and copy it to save a copy for Majordomo Executus.  This way you can play Amara for survival before you have all of the Majordomo package ready.

Shadow Visions - Get an extra copy of any of your spells

Archbishop Benedictus - If you drew most of your deck using the plentiful draw in this deck and are Ragnaros, play this to avoid taking damage from fatigue so that you can have plenty of turns to use your Ragnaros hero power.  This can be a win condition by itself as you can use your removal and Ragnaros power and win when your opponent runs out of cards faster than you and takes fatigue damage

Questing Explorer - More card draw, very useful for getting all your Majordomo Package pieces in hand

Acolyte of Pain - More card draw, very useful for getting all your Majordomo Package pieces in hand

Coldlight Oracle - More card draw, very useful for getting all your Majordomo Package pieces in hand

Zola the Gorgon - You can use it to copy an extra deathrattle or Highlander card, or play Amara, Warden of Hope and copy it to save a copy for Majordomo Executus.  This way you can play Amara for survival before you have all of the Majordomo package ready.

Mulligan Guide

Always keep the quest.  The following cards are good to keep as well but it depends on whether you think you are going to face an aggressive deck or not

(don't keep against aggro)

(don't keep against aggro)

(don't keep against midrange or control)

(don't keep against control)

Hope you enjoy this deck and let me know if you have any questions or comments.