Do the forest goblins first then, seen to much night gobbo armies in 8th!
That'd be because Night Goblins are the best gobbos in lore, design, and entertainment value and I'll fight anyone who disagrees.
But yeah,
Forest Goblins it is.
I hope you like spiders and mortal wounds. Again, we'll use my place's standard 125 Wounds for the army size.
Big dilemma with this one was deciding if it was worth taking the Spiderfang Venom Mob battalion for this army. On the one hand, its
Embodiment of the Spider God rule is probably the single best buff for gobbos in the entire army and for Forest Gobbos we already wanted an Arachnarok spider, a bunch of Spider Riders, and a Forest Goblin Boss anyway, but
three Arachnaroks? That's an expensive pick, not only in terms of draining the wound limit but also in actual monetary costs as each one costs about £36, so that's quite expensive. However, each Arachnarok only costs about £4 more than the alternative, filling up those free wounds with regular riders, so really you're only spending around £8 extra to get
Embodiment of the Spider God. Furthermore, the rule is that good that in larger games such as a 125 Wound game, it almost feels like a must-have. So I'd say go for the Battalion.
1 Goblin Big Boss on Gigantic Spider (6)
3 Arachnarok Spiders w/ Catchweb Spidershrines (48)
38 Forest Goblin Spider Riders [3 units] (124)
Honestly I don't think I've ever designed an army that's so simple to build yet would be so visually and practically impressive. Seems little at first glance, but remembering that each Arachnarok is an individual monster carrying a full 2-spell Wizard each, the power is clear. Not to mention the image of three titanic spiders blasting along the battlefield with a downright insane amount of smaller wolf-sized spiders scurrying between the giants' legs like a tide is an undeniably impressive sight, plus the Boss' gigantic spider in the centre really serving to complete this image.
But in addition to that, there's some genuine practicality to this army that, unlike basically every other themed army I've ever designed, gives this army a real power in the meta-game that to be honest, I would fear. (Mainly because the Spider's strategy completely and perfectly counters my own.) This army is all about Mortal Wounds. While the spiders may be frail compared to most cavalry with their weak 5+ save, their ability to cause a Mortal Wound instantly on a Hit roll of 6 with their spider fangs is quite powerful, especially as each spider gets to make 2 attacks with their fangs each. Factor in the Arachnarok riders' Gift of the Spider God and each Mortal Wound caused by these fangs doubles. Finally, the
Blessing of the Spider God from the Big Boss gives an AoE buff that causes these Mortal Wounds to occur on a 5+ instead of a roll of 6, doubling the Mortal Wound rate. With this, and assuming you split your Riders into equal sized units of 13 (with one unit being only 12, but ignore that one) and all 13 Spiders manage to pile in to attack, you're looking at an average of
17 Mortal Wounds per unit before normal Wound rolls. Not to mention that those normal Wound rolls get a +1 modifier from the Battalion's
Venom Surge rule, bringing even more pain. In addition to these Mortal Wounds from the bites, each shaman can cast 2 spells, so after ripping off a Gift of the Spider God, it may be effective to have them all launch a basic Arcane Bolt at whatever unit you want to fuck up today, resulting in a further 3D3 Moral Wounds, easy to do with Bolt's Casting Value being only 5. Oh and speaking of Casting Values, Gift of the Spider God only has a Casting Value of 4! I only know one other spell that's so easy to cast and it's not nearly as game-breaking as this, (it's our Curse of Fates, by the way.)
It's also worth mentioning
Embodiment of the Spider God, it is the main reason to take this Battalion rather than just dropping one or two of the Arachnaroks for more Spider Riders. With this rule, any unit within 8" of
any Arachnarok becomes
immune to Battleshock. Holy sheet, Unbreakable Goblins!? Goblins are meant to be cowards, these guys are running a Bravery of 4 for Pete's Sake! But nope, now any hope your enemy may have of using Battleshock to cripple your army at a range has been utterly dashed because your Goblins are just that fearless. Ouch.
Worth noting, your Riders have a movement of 8" making them very fast at crossing the board, but when they're still making their way over and you're up against somebody shooting at you while you try to make it, it may be worthwhile to give these little guys a Mystic Shield. With Gobbo Shields too, you'll be rocking a respectable 4+ Save, enough to see you to your enemy's line where the Mortal Wound-fest can begin.
Finally, the major problem a lot of high-number armies face is the issue of terrain, large units and monsters tend to get hindered by terrain blocking their path. But wait, literally everything in this army can just walk over any terrain piece as if it were not there because of their Wall Crawler ability. Meaning that your opponent can't try to bottleneck you to lessen the number of attacks you can get in, a common defensive strategy that I've used a lot. Naturally this should all highlight that between your ability to ignore terrain and your ability to totally ignore armour, this is a godly counter to defensive armies. (Such as my Temple Guard army or the Empire army I designed here a little while back.)
Strong against: Literally any army that has high armour as its main strength, almost all defensive armies fall into this category. Fast movement and Battleshock immunity gives them a strength against slippery ranged armies like Skinks and Wanderers too.
Weak Against: People who can block Mortal Wounds such as Chaos Warriors or Nurgle daemons, fast Glass Cannon armies may also have a distinct advantage as they die en masse anyway so your own damage will have little effect, meanwhile they would take advantage of your relative frailty and smash you first. Anti-magic armies may also prove to be an issue as blocking your Gift of the Spider God and Arcane Bolts can prove to be a problem, though you still have six spells so you'll likely get some off. Beastmen may be particularly good at this as they can do a real number on your spellcasting, the right builds being able to net you up to a -5 to Casting rolls as early as Turn 1, plus the fact that they're the perfect Glass Cannon army that I already mentioned would ruin your day.