NElf is a great ally, as allmost all of your units also benefit from the night boni, which also makes the Nyctan Cult a nice option against NE, as it counterbalances their night bonus.
UD is another great ally, due to the DK being able to heal some of your units, like the Nocturnal Terror.
Consequently use 'Unleash them!' from your Kennels to scout nearby areas, pull creeps or just to defend the base against rushes.
NT & Dusk Aviators
Max the Predator's Aura & Call, rush for T2 and get dome DAs. As soon as you get T3 and research 'Focus' for them, in combination with the Nocturnal's buffs it will drive their IAS to an insane rate.
If building a Mischief Factory, you can spam Raid Technicians and build a circle of Mungos close to the enemy base with the Technicians inside, so they can repair, safe from meelee attacks. Additionally, you can upgrade them and upgrade some to Cobras for aa coverage.
Against invisible units:
Dust of Appearance, Arctic Alpha's 'Perception', Research 'Surveillance' for your towers.
Against casters:
Hexecutioners (Spell-immunity, cleanse, Manaburn), Vermin Hags (Mass dispell at Adept level), Foul Cherubs (Coriaceous Skin)
Against air-unis:
Sagittarians, Raid Technicians -> Cobras, Towers, Angel of Deceit's 'Hellish Conversion' also 'Misguidance', Foul Cherubs win against Wyrms, Gryphons, Chims. Agony Orb (Market)
Against ranged/siege units:
Eclipsefiends(very fast and high dps, 'Bloodthirst')
Against buildings:
Raid Technicians -> Mungos, Cobras, Shatter Colossi
Recovery possibilities:
Vampire Potion & Fed Caddle & Hp Potion (All Market), Mythcultists (Superstitious Aid), Angel (Hellish Conversion), Nocturnal (Call of the Carnivore), Foul Cherub (Coriaceous Skin)
Escape tactics:
Sagittarians' 'Ambush', Staff (Market), Haunting Scarecrow's 'Scare', Nocturnal Terror's 'Thriller'
Disablers/Debuffers:
Arctic Alpha (Icicle Hook, Ulti), Angel (Abacinate, Misguidance), Nocturnal Terror (Rabid Strike), Haunting Scarecrow (Scare, Head Throw), Mythcultists (Heresy at Master Level), Eclipsefinds, Foul Cherub (Both on attack after Upgrade)
Summons:
Fed Caddle (Item from Shop), Yard/Guard Wolf ('Unleash them!' at the Kennels), Fungus (Vermin Hags' 'Fungal Bolt'), Underworld Guardian (Angel's Hellish Conversion)