Heavenly Hippoe, Gabriel and Angelic Gory appear as peons and support. Angelic Sleipnir appears as the boss after enemy base is damaged. Angelic Sleipnir also appears as the main threat, due to his knockback ability and averagely good status. Sleipnir becomes especially perilous after teamed up with Gabriel and Angelic Gory. They will break through player's line easily if they aren't on their toes.
Angelic Sleipnir has quite long range so bring Bahamut and any cats that have a longer range than 372. The player should consider to bring Artist Cat as a meat shield (if he is Level 30+). Also, choose cats who has AoE skills, good DPS and range, because you always want those peons killed ASAP.
For first time players: Since this is probably the first time you've encountered Angelic Sleipnir, it is recommended to spam any Anti-Angel Cats. Bahamut should take care of Sleipnir, so don't worry about him.Also,any true form is recommended,especially the flying cat. If possible, Kalisa helps very well for this stage, she can clear through the Angelic Gorys with a breeze.
For this strategy to work you need God-Emperor Dioramos level 30+ and Ramen Cat level 36+. These cats alone can take out the boss. You MUST use Dioramos's final form for this to work. The battle will start and you need to upgrade your wallet ONCE. ONLY ONCE! If you upgrade it more then by the time you spawn Dioramos you will have 3 heavenly hippoes out. Use Ramen Cat to stall the heavenly hippoes and weaken them. Even level 40 Dioramos doesn't 1 hit the heavenly hippoes. 1-2 hits from a high level Ramen Cat will kill them after that. From there on out just meatshield with the Ramen Cats and do damage with Dioramos. Sleipnir will get knocked back by Dioramos, along with the peons/support. Ramen Cats should stack and deal a lot of damage too. No combos are needed but research combos help. My cat levels for this level were Dioramos level 39 and Ramen Cat level 40. Good luck! Even though you won't need it!