Entropy 13

• Wave 1 (Boss Wave)
  Elvoret & Spark Eye. Both of these bosses get more dangerous the longer they are alive. The Elvoret's stackable framed buff (Tower's Dark Wings) increases its own HP damage dealt, Debuff Evasion and ATK, while it lowers your DEF, iBRV and mBRV. The Spark Eye increases it's ATK every time it does Capacitance, and on the third cast it also increases its DEF.

The best strategy is to take out the Spark Eye first, as the familiar Supercell (BRV Gain + AoE BRV + HP (split) attack) is extremely devastating and can wipe your party. Keep the BRV of the Elvoret in check and all should be fine.
Debuffs Inflicted: DEF/iBRV/mBRV Down

• Wave 2 (Boss Wave)
  Two Jeweled Turtle (Fire Resistant). They gain massive BRV when they go in hiding so BRV shave it at all costs or you will likely die. Their only AoE attack is a BRV+HP Attack, so brace yourself for this. Upon using Jewel Bullet, they buff mBRV up, cleanse unframed debuffs, and also have high turn rate if breaking or attacking a broken target. Be careful or this will kill your run.
  Debuffs Inflicted: Delay, Sap

• Wave 3 (Final Boss Wave)
  Marilith Gloria (left) & Marilith Tempest (right). Kill the Marilith Tempest (right) first, as it enrages while the Marilith Gloria (left) does not.

These two have a lot of AoE attacks. The Maralith Gloria buffs itself, inflicts HP Poison, and has high turn rate when breaking or attacking broken targets. The Marilith Tempest meanwhile is a BRV+HP machine. Thankfully these two have deceptively low HP, so balance bursting them down while also making sure you have enough heals left to stay healthy in this last wave.
Debuffs Inflicted: Physical Resist Down, Thunder Resist Down, iBRV/Def Down