Army list
Main body
With army composition I wanted to have a base of units which would be re-rollable steadfast/stubborn. In 7th Ed, I used treeman, eternal guard and a BSB to great effect as anvils. As such, I would like to apply the same approach to this army whereby I have a couple of Treeman anvils, which will be in a staggered formation with respect to dryads and eternal guard. I am mulling over whether I want to split up the dryads unit to provide two flanking units and place Lothlann in the unit of Eternal guard, but for now I think this will be ok. Having a shadowdancer in the unit of eternal guard will greatly increase their combat effectiveness, not only due to the increase in killing power but also due to Woven Mist.
Advance force
The two units of glade riders and waywatchers will be in charge of warmachines and taking out chaff. The new rendition of glade riders provides some uncertainty in battle plans, but think that overall: having them fail to turn up when you want them will ensure for some laughs as well.

Support
The wild riders will be the last unit I deploy. Their duty is to wreak as much havoc on the enemy as possible. For horde armies, I think they will work really well, same as for hitting small elite units. Their new rules make them so powerful... The sister bus will house Lord Arlas at first. I want to give him some protection such that he can survive to obliterate the enemy. Aside from that they will provide equally good protection for Lady Morlanna.
Characters
Reading the fluff of Modryn, it begged for Arlas to take the spirit sword and trickster shard combination. This in and of itself provides some interesting features: Arlas can serve to take out a unit of heavy cavalry (chaos knights, blood knights etc), but also to take out enemy super characters and monsters. Yet he also has some downsides: absolutely no protection, lack of mobility and a severe lack of strength when facing tougher opponents. By placing him in the unit of Sisters, he will protected somewhat due to Curse of Anraheir and Lichebone Pennant. By mounting him on a stag he gains great mobility (though negates fast cav rules for sisters) and some extra hitting power. Yet he will still have trouble against tougher opponents, which is where Morlanna comes in.
Making Morlanna a level 4 shadowweaver is not only fluffy, it provides some interesting opportunities. Her preferred spellset would be: Miasma, Withering, Pit of Shades and Mindrazor, but really any combination of spells works well for the army (though Mindrazor is a must-have). Guided by Loec, I plan on having her charge a heavy cav unit or super character during the movement phase and subsequently cast Miasma to lower the opponent's WS. This does two things: lower the enemy's potential to hit in CC, but also allows me to swap places with Arlas. If Morlanna has Mindrazor, I will not hesitate to cast it with fury on Arlas. Alternatively, if I don't have Mindrazor I could target a different unit with Miasma to lower Initiative and still swap in Arlas and then subsequently hit the target unit with Pit of Shades.
Modelling and colour
The colour theme of the army will be dark and grey and I plan on making some proxies for the main characters, which I am quite excited about.
For Lord Arlas, I am thinking of using the body of a farseer with a wild rider head. His stag will be a thunderwolf. I would like for Arlas to be standing in front of his mount, sword in hand with the wolf circling behind him.
Lady Morlanna on the unicorn, I am thinking of using the spellweaver and adding some pegasus wings. In terms of fluff, I think I will change the unicorn to something like the blessing of Anath Raema which gives her the same rules as a unicorn. A bit of a workaround but hopefully will provide a nice model.
Wychwethyl, I would like to convert the shadowseer model. By getting rid of the jetpack, sword and replacing the head, I think you can really make a fluffy shadowdancer.
Lothlann, will be converted from the waywatcher with the raised dagger.