You guys break my heart not knowing what the Karagh is.
It wouldn't make much sense as a tome unit (AFAIK) since those seem to be ostensibly summons and equipment/enchantment to improve your units, along with elemental/magic-based things.
It wouldn't make sense for dwellings, either, as Karaghs were a uniquely Goblin-derived unit. They're also mindless beasts.
Let me explain:
Way back when, the goblins were sort of... crap. They were weak, they were vulnerable to pretty much everything, and outside of underground they just couldn't contend with the other races. The other races had undead that could ignore their injuries, giants that could heave boulders, heavy armour and brute strength to overwhelm their foes, could cross water or freeze rivers or any number of other things. Goblins had... poison that was mostly derived from them living in cesspits and long sticks. So they had to get creative if they wanted to keep pace. They had to find bigger things. Stronger things. Things that weren't very smart - things they could maybe control. Giant insects, trolls, wyverns and wolves. But deep, deep underground, in the places where light has never reached, there was something even more dangerous and the Goblins were the only ones stupid (or crazy) enough to try to handle it.
Enter the Karagh. It is a grotesque gaunt-yet-fat mindless beast that roams the lightless caverns of the underground. When it catches a whiff of blood, the sound of voices, or any other sign that prey might be nearby -- does it hide and lay an ambush? Does it crawl across the ceiling? Does it have some special unique ability to cleverly wound its prey? No. It screams. It screams and howls and races through the underground paths faster than dragons can fly
. All you get is the ungodly screams of some unthinkable horror in the dark echoing off the walls until it bursts from the darkness and savagely clubs or devours everything within arm's reach, killing in a blind frenzy.
It's not magic. It's not some special creation or have some sort of awesome clever ability. It's just a thing of horrors that only the Goblins could manage to capture. And when they need to, they point it towards their enemies and let it out - and hope that it doesn't think to turn around. It was the single coolest thing that Triumph came up with and, at least for me, it epitomized what made the Age of Wonders Goblins unique: the ability to use many, many other species to fight their battles for them. The Karagh filled out that roster by being a huge scary beatstick that was the undisputed ruler of the underground.
It's frustrating to me, then, that Triumph moved away from that into making the Goblins more generic so that they had similar stats to, say, an Orc or a Draconian - when really it should just be goblins using every tool in the box to get a leg up despite having a statistical disadvantage. They're the scrappy underdog of scrappy underdogs (lore-wise) and I really found that appealing.
Unfortunately with the desire to increase customization the strong theming of the Goblins was lost and in AoW3 they were practically interchangeable with other races until DLC gave them a few tweaks - but even then they never brought back the Karagh.