Spectra is filled with Ghost-type Pokémon, for the most part. Since one is Bug/Poison, we'd bring a Fire-type. Also, since there is a Ghost/Fire, a good Water/Ground type. As for the Ghost/Flying, an Electric type should work out good. Of course, other than these side options, note that Ghost is weak to Ghost and Dark; immune to Normal and Fighting; and deals no damage to Normal.
Personally, we brought along our trusty Jolteon, Emboar, Quagsire, Haunter, Jigglypuff (better to have an immunity than resistance), and the Sneasel we found earlier, but we gave it a few Link-boosting items to power it up some.
Battle: Nobunagas Army (Turns: 15)
|**Win Conditions**||**Lose Conditions**|
|Beat all of the enemy Pokémon.||Have your Pokémon KO'ed.|
Mismagius is weak to Dark and Ghost, and is immune to Normal, Fighting, and Ground (by ability). Its attack is Shadow Ball, which hits a target two tiles away, may lower Defense, and does extra damage to Ghost and Psychic. Its ability is Levitate, which immunizes it from Ground.
Scolipede is weak to Fire, Flying, Rock, and Psychic. Its attack is Venoshock, which hits a tile two tiles away and the two left and right of there, and will do more damage to poisoned targets and Grass Pokémon. Its ability, Poison Point, may let contact attackers get poisoned.
Lampent is weak to Ghost, Dark, Rock, Water, and Ground, and is immune to Normal and Fighting. Its move is Flame Burst, which hits a tile two tiles away and all diagonally-adjacent tiles, and does extra damage to Ice, Bug, Steel, and Grass. Its ability, Flame Body, may let it burn contact attackers.
Drifloon is weak to Ghost, Dark, Electric, Rock, and Ice, and is immune to Normal, Fighting, and Ground. Its move is Astonish, which attacks an adjacent enemy and pushes them back, may cause flinching, and deals extra damage to Ghost and Psychic. Its ability, Dodge, may let it evade an attack and then lower the enemies' stats.
Dusclops is weak to Ghost and Dark, and is immune to Normal and Fighting. Its move is Shadow Sneak, which hits an adjacent enemy, and deals extra damage to Ghost and Psychic. Its ability, Interference, may lower nearby enemies' accuracy.
Misdreavus is weak to Dark and Ghost, and is immune to Normal, Fighting, and Ground (by ability). Its attack is Astonish, which will attack an adjacent enemy and push them back, may cause flinching, and deals extra damage to Ghost and Psychic. Its ability is Levitate, thereby immunizing it from Ground.
The battle strategy, in itself, is pretty ordinary. Pair your Pokémon up with the one whose weaknesses it can abuse and attack. Heal as needed, and never forget Warrior Skills.
The terrain also looks ordinary, but is not so. Firstly, those Misdreavus statues on the field can move, as can those fireballs. We arequite sure that if you get hit by one, you'll be damaged. Of course, the fireballs have such a long Range that you're almost never out of reach, so just keep those healing items handy. Also, the fireballs will inflict statuses on you.
Eventually, you'll conquer the sixteenth kingdom, and thereby have conquered all of Nobunaga's kingdoms. Or so we were told...