Belial

Triggers 100% - 51%

Lemegeton - Entry

19,999 plain DMG to all allies

Make sure your frontline has 20k+ HP

Goetia - Every 3T

16 hits to random allies (2400% DMG total), inflict Slashed and Supplemental DMG

15m DMG to cancel the omen. If cannot cancel, tank it with Veil and guard.

Lemegeton - Every 6T

1 hit 500% DMG to all allies. Dispel 2 buffs

35 hits to cancel the omen. Can be hard for Kengo to do 35 hits, so can tank it by guarding.

Asmodeus - 65%

13 hits to random allies (2200% DMG total)

Dispel to cancel.

Triggers 50% - 6%

50%

Upon entering 50% for the first time, Belial gains 3 elemental shield.
These shields absorb the respective elemental DMG

Deal 15m DMG of any element that is not absorbed by the shield to clear all 3 elemental shield.

Anagenesis - 50%

100% DMG to all allies. Deals 10,000 plain DMG for each stack

You can remove the shield as long as its not the dark shield. He will also deal 10k Plain DMG for each stack.

Goetia - Every 3T

16 hits to random allies (3840% DMG total), inflict Slashed and Supplemental DMG

FC to cancel. If cannot cancel, can use a single sub with dodge (E.g. Seox S2 + Dodge) or tank with Veil + Guard.

Lemegeton - Every 6T

30,000 DMG to all allies, inflict Skill Sealed and CA Sealed

Dispel to cancel.

Triggers 5% - 0%

Lemegeton - 5%

100% DMG to all allies

Prepare your bar if needed for the final turn next or just guard to minimize even more DMG.

Anagenesis - N

Party Wipe

Do all your stuff and burst.

Sample Grid

Characters

You want to bring 1 character that can delay without pressing skill (E.g. Lich, Tanya, etc.), apply debuffs (E.g. Lich, etc.), and provide some survivability (E.g. Fediel, Lich, etc.).

For reference, a common setup would be Kengo, Fediel, Flex, Lich, Flex, Flex.