This is, much like your initial fight for Chrysalia or even Greenleaf, a spot where a Fire-type can really shine- both Cubchoo and Drillbur have trouble with Fire attacks- Drillbur loses out big from burns with its relatively weak defenses, and Cubchoo is made of ice. You won’t find yourself needing the excellent mobility you set up to deal with Illusio’s map as much as you might have- but you want to have it here anyways- after all, this is going to be an excellent source of increased Link rating, and you want to have as strong an invading force as you can manage to attack Illusio. As an added bonus, the Flying-types and Levitate pokemon you probably bulked up on prove their worth even here, as they are completely immune to the Dig attack that Drillbur tries to punish you with- as long as you keep your Fire-type from getting attacked by Drillbur long enough to pull off a hit against it, you’re good.
Be wary of the evasive capability of the Psychic pokemon- Scraggy proves a great choice with the never-missing Faint Attack as its battle maneuver, effectively more resilient even than a Pineco thanks to its still fairly large defenses and typing that makes it as good as transparent to the attacks of Ralts and Kirlia.
Abra proves more of a nuisance than any kind of threat on this battlefield, as all it can really do is move around and occupy spaces.
If you’re lucky enough to break the Iron Wristband that Aya’s Cubchoo holds, that will make your subsequent attack on Illusio a bit easier, so keep an eye out for the notice of achieving that.
This battle shouldn’t take too much out of you, not with your forces loaded for bear (or rather, Gallade). Unfortunately, you can’t gain any new Warriors out of it, so don’t worry about placing new Psychic-equipped Warriors anywhere (much less a Drillbur or Cubchoo).
Victory results in a rousing cheer that Chrysalia will not fall to these invaders- and a nice big chunk of Link % for all your Warriors who participated.
Once you have finally left the victory screens, Aya declares you ‘impressive’, claiming to have seen your love for your Pokemon. With that ascertained, she now believes you strong enough to truly bring a challenge to Kenshin- a battle she looks forwards to.
With Chrysalia defended, Oichi exclaims over the wonder of such powerful Warriors coming to your kingdom to do battle- but you’ve succeeded, and saved ‘the day’..... and then something starts happening. Something very familiar- but to someone unexpected.
Congratulations! You’ve evolved....?!?