Do allow me to expand on that a bit...
Karu is somewhat unique as far as dungeons go. You give an item to the altar, which is actually a form on NPC and not simply a tile on the floor, but that hardly matters. You enter the regular dungeon inhabited by stone zombies and pot belly spiders - stone zombies resemble golems, and pot belly spiders look like a collection of kitchenware turned into a golem ("pot" belly isn't just a catchy name). When you kill the zombie/spider during the dungeon, they drop body parts. Pincers, fangs, venom-sack, pot, and something else I think there's 5 parts. When you collect a regular piece, then you re-enter the dungeon using that as the sacrificed item. This brings you to "Karu fangs ruins" or whatever body part. The boss of this run will have glowing fangs (or whatever) and it will drop a glowing body part. Then you go BACK into the dungeon, using pincers, and you collect glowing pincers from the boss. When you finally have all 5 glowing bits, you trade them in for a full glowing statue.
The full glowing dungeon is a fresh sort of hell. The original boss, the Stone Horse Keeper, becomes a miniboss, and the final boss has like 6 stone horse keepers as extra mobs! Instead of spiders, you're dealing with zombie ghosts - that's right, zombies so badass that they've died again and become un-un-dead zombie ghosts. And then the infamous, terrifying, Golden Mask Ghosts. Like something from an eldritch horror, they occupy a golden mask the size of a human's face, with a flourishing aura of vaporous power flowing out behind it. They are mostly immune to all attack, with natural shield, heavy stander, and mana deflector of fairly high rank, they will totally ignore your attacks and proceed to fuck up your day all over the dungeon floor. The only realistic way of combating them is to have archers spam magnum shot and/or firebolt to keep the damn things at a distance. Perhaps the most terrifying thing (to me) is that they are non-aggro until attacked. They will patiently circle you softly, watching, waiting, observing. Calmer than the grave and more patient than the madness that seeps into your bones, they softly wait until you crack, until YOU become the unwilling instigator of your own demise.
The Golden Mask Ghosts also have a very powerful trick. In some rooms, they "rest", becoming intangible for a period of time and returning with their HP almost entirely restored. If you cannot kill them quickly, then they recover. Archers are essential here, as they can deal black wound damage, which will NOT recover. Although even archers fail at the titled ghosts. These have extra protection, which results in a lower wound rate, making their only weakness into a pitiful attempt. The only real way to combat these titled ghosts is simply to have the entire party swarm on them and do as much DPS as fast as possible.
Rewards are nice though. VERY nice. In two successful runs we performed, we were gifted with 1 copy of the Exploration Page 3, used to unlock Ice Spear, a Dragon Fang sword (two handed mega-blade, one-handed for giants), Red/Blue upgrade stones, and some very powerful enchant scrolls that we couldn't really utilize. And gold. Piles and piles of pure gold coin.
So are you interested? Yes.
If you cannot contribute, you can contribute. The rooms contain many multi-aggro mobs and sometimes require instant-contact massive DPS to win. You can contribute by coming into the room, gaining aggro from monsters, and then playing dead. This means that the monster or two are suddenly not a threat to the real fighters, and they can focus on immediate concerns and then deal with your aggro. The resting rooms can also benefit if the non-contributing teammates do multi-casting of firebolt, smash, magnum, or windmill, in order to deal as much damage as quickly as possible from the whole party on a single target.
Plus, more members doesn't hurt. At the worst case, you can sit outside the current room and leech exp. It will not hurt the party's fighting at all, you get free exp, there's another chest at the end with potentially amazing rewards, and in the worst case, you can come in with a phoenix feather, revive someone, and immediately play dead. Party Healing and all bard buffs will also work through walls, but we'll only need ONE dedicated bard. No overplaying please.