To Obtain Desco's Epilogue you must:
1) Complete the first 9 episodes
2) In Episode 10 Complete Stages 1-6. DO NOT COMPLETE 10-7 which is the final stage
3) If you haven't done so already, call a Senate and unlock the "Legendary Tree" Evil Symbol and place it somewhere on the map in Cam-pain so all squares are visible. The Pattern is +.
4) Go back to Base and Save your game. You have multiple slots so what I did was save the game in slots 1-5. Only one epilogue can be unlocked perm playthrough which is why we use multiple saves
5) Go back to the Cam-Pain
6) Place Valvatorez on the L square and Desco on the one of the other 2 squares. The middle DOES NOT count.
7) Hit LT or whatever button it is to "Dispatch an evil deputy" and walk up to the Legendary Tree and hit the Action button to interact. Set Desco to "Step-Sibling"
8) Go back to the Base and Save your game to one of the 5 Slots you saved Earlier but ONLY ONE. (You can also change your save icon in settings to the character you doing the Epilogue for in Settings to make it easier to identify saves)
9) At this point Quit and load up one of the other saves and repeat steps 5-8 for each character. So once you are done, you will have 5 Saves with all 5 characters set up at the Legendary Tree. Skip if Completed already through one of my other Epilogue Guides
10) Now each character has a specific requirement to unlock an event needed to get the epilogue. Check each characters achievement for their individual task. Desco's is to protect her 10 times.
11) You will need to place Valvatorez(Leader) and Desco in the Defense Fortress (Dont be like me and confuse it with the Heart Cannon).
12) Load up Stage 1-1, Send Valvatorez and Desco out and place them side by side. Use Defend on Valvatorez. Bring out a ranged Character, preferably a weak one who wont do much if any damage and have them attack Desco. Valvatorez should Jump in front and take the attack. I believe you can only do 2 blocks per turn.
13) After you have completed 10, Finish the Level and head back to the Legendary Tree. An event should occur.
14) Now Complete 10-7 and you should unlock the Epilogue after the Credits.
15) You will be prompted to Save after the Epilogue. You can choose to do so if you wish. Obviously only save to the dedicated save for that character if you do.