How to beat the Castellum
Leviathan begins in the huge ornate plaza of The Castellum. This is the central hub of Destiny 2’s Leviathan raid and serves as a sort of intermission encounter. You’ll have to clear it several times throughout the raid, so you're going to want to do it as quickly and cleanly as possible. The good news is it's a fun, hectic fight with a ton of adds (raid shorthand for additional enemies) to gun down.
After flying into the raid, climb to the top via the jump jet boosters, and walk past the ranks of Cabal guards (yes, they will shoot back if you fire first). The Castellum is through the big door at the top.
There are four doors in the Castellum, each with a plate marked by one of four symbols: sun, dog, axe and cup. (These symbols will come up throughout the raid, so make a note of them.) Each of these doors leads to one of the raid’s main fights. The sun door is left of the entrance, the cup door is straight back, the dog door is near the middle, and the axe door is off to the right.
The order of raid encounters varies from week to week, but the process for accessing them is the same. Your goal is to kill three orange-health ‘standard bearers’, bring the standards they drop to the plate by the door you need to open, and prevent ‘standard liberators’ from stealing your standards. Once three standards have been placed, you can proceed to the next encounter.
Retrieving the standards
Start by killing all the Cabal in the area. While you're doing that, figure out what door you're opening. You can tell from how well-lit the symbols above the plates are. Next, split your team into two groups: a group of two to grab new standards, and a group of four to defend your plate. Running three and three is also fine, and don't be afraid to change it up if you're having trouble.
After a few waves of Cabal, a bearer will spawn. The symbols on your plate will tell you which door the next bearer will spawn from. There will also be a text notification in the bottom left. So, if you’re opening the sun door and your plate is showing a dog symbol, you’ll need to head to the dog door near the middle, kill the bearer there and retrieve his standard.
Defending the plate
Meanwhile, the defending group has to fight back hordes of Cabal, taking care to eliminate liberators as quickly as possible. Make good use of roaming supers and power weapons, and whenever a new standard is placed, pile onto the plate. It will temporarily grant the 'force of will' buff to anyone on it, enabling you to shred through any remaining enemies.
Every few minutes, special psions called ‘loyalty councilors’ will spawn somewhere near your plate. These are obvious from their giant bubble shields and their arrival is also noted on-screen via text. You need to kill them as quickly as possible, otherwise the liberators will gain immunity shields and march right on through and steal your standard, setting you back a step. You can’t shoot through the councilor’s shields, but one melee will take them out.
Continue retrieving standards and fighting back Cabal until all three standards are in your plate. This will open the way to the next encounter.
Next page: How to beat the Royal Pools.