No blue on the free summon.
Abyssal Duma wasn't too hard. The map basically forces your foes to march toward you in single file.
Abyssal Naga took a bit more work, requiring some skill and seal changes and more careful positioning to make things line up. Switched Def Smoke to Res Tactic on Ares, swapped out Armored Boots for Distant Defense on Legendary Hector, and gave Ophelia Drive Res seal, all to help Hector soak up a lot of damage. One particular foe carrying Windsweep turned out quite useful, as he blocked other melee units from attacking Hector (most notably the red Armorsmasher cavalry following close behind). Ares and Ophelia picked off all the foes Hector didn't or couldn't handle, with support from Adrift Azura.
Abyssal Roy and Julia I haven't figured out yet. My attempts at Roy so far have ended with my team scattered all over the bottom half of the map right as Roy moves down into it with a horde of enemies following close behind. With Julia, my current team seems to have hit a dead end. The first few turns go excellently, but in the final few turns my team gets cornered by Julia and her last few reinforcements in the bottom left corner of the map, with not enough of an opening to take out Julia and not enough safe tiles to have everyone survive.
Back up to 200k feathers now, so it's time for me to decide who's next to +10. Aversa would probably the wisest and most practical investment, but there's some other units I'd love to +10 too - Catria, Cherche, Est, Lilina, Nino, and some others. I could also start building regular Adult Tiki since I lack properly built dragons. Winter Cecilia I really want to get merged up too, but I don't think I can justify spending my grails on her before Aversa.