Extreme Evolution is a buff that is obtained in the Shadow Labyrinth. It lasts for 2 hours once used, and it will only stay in your inventory for 2 hours. If your inventory is full the buff will be stored in your 'Gift & Reward Storage for up to 6 days.
The Buff itself applies to Digimon of three classes, those three are Mega, Side-Mega, and Burst-Mode. For Digimon of the Mega and Side-Mega class it applies a +50% damage boost to them. For Digimon of the Burst-Mode class it applies a +25% damage boost to them.
Note: The Extreme Evolution buff will not apply to Spirits or Digimon of similar class, nor will it apply to 'X-Digimon'