If your defensive squad survives an enemy attack, each surviving character will have a new negative effect applied to them during the next battle known as "Exhausted." The effects of Exhausted will stack, cannot currently be cleared, and the effect will persist between battles. Defending characters can have up to a maximum of 4 Exhausted applied from Knowhere Siege. Each Exhausted lowers a character's Damage, Armor, Resist, Focus, and Damage Reduction by 20%. So, for example, if your Gamma team survives a battle with the Underworld team, all five of your characters will have +1 Exhausted for the next battle, If four of them survive that second battle, they have +1 Exhausted applied for the third battle for a total of 2.