Welcome to the Demonology Warlock guide written by Veilian. I joined Method in Shadowlands and I've been playing Demonology since the beginning of BFA. In BoD and TEP I almost exclusively played Demonology for Mythic progress.
Demonology is a cooldown based spec where you do a large burst of damage every 1.5 minutes with your cooldown, Summon Demonic Tyrant, and outside of Tyrant, you do cleave damage.
What has changed
The biggest changes from BFA to Shadowlands is that they reworked how your level 50 talent, Demonic Consumption works. It now drains a percentage of all your demons' health, instead of consuming all of your imps to improve your Tyrant.
Tyrant also received the effect of the Baleful Invocation Azerite Trait that refills all of your shards when you summon your Tyrant. They made our rotation smoother and reworked the Explosive Potential into a legendary. There was also an undocumented change to Demonology imps that they last for around 40 seconds when you are not in combat, making it easier to carry over resources from pull to pull in dungeons.