What is overpowered about them? What are their spellbooks if you dont mind typing out.
Well, first there is their permanent ability to leech on everyone's rituals, that alone gives a lot of doom points.
As for spellbooks, there is the thing that you can get 3(!) of them in the first round without much of a caveat.
The requirements are:
Another player performs a ritual of annihalition OR another player has 15 doom points.
Earn an elder sign
Own three or more elder signs
As an action remove your controlled gate in your starting area
Any great old one is killed in battle.
Awaken Ubbo-Sathla
You can easily get 2,3 and 6 in the first round and still come out in the second action phase with enough power to hold your own. Just sacrifice your high priests which you will have enough because your spellbooks are:
Soulless (ongoing) When Captured and Sacrificed, your Cultists provide 0 Power (instead of the normal 1 Power).
Terror (pre-Battle) Choose one:
1) Your enemys Combat total is reduced by 1 per Proto-Shoggoth in the Battle.
2) Your Combat total is increased by 1 per Proto-Shoggoth in the Battle.
Martyrdom (post-Battle) If your High Priest is Killed, all other Kills inflicted on you in the Battle become Pains instead.
Idolatry (Action: Cost 1) Select an Area containing another Factions starting Glyph (even if that Faction is not in play). Move any
or all of your Units in adjacent Areas into the selected Area.
Hierophants (ongoing) When you earn any Spellbook (including this one), immediately place a free High Priest at one of your Gates. If you have no High Priests in your Pool, instead advance Ubbo-Sathlas Growth counter by 1.
Tablets of the Gods (Doom phase) When you perform a Ritual of
Annihilation, you also receive 1 additional Elder Sign for each of your
High Priests in play. Then, Eliminate those High Priests. This is not optional.
Obviously you pick Hierophant first. Followed by Soulless and Martyrdom or Terror. I went with Martyrdom.
The thing is at this point you are already rather unattractive to be attacked by your enemies. Capturing your acolytes is worthless and as long as you have a high priest in position you are more or less unkillable.
The rest of your spellbooks are dependent of others more or less but in my experience they shouldn't be much trouble. The rule book states that you'll get all your spell books at the end of the fourth round earliest...which is bullshit. I got all of mine at the end of the second or third round. Idiolatry was my last and the only one I didn't use.
I actually had to not build a gate (even though I could have) just because I knew it would have put a huge target on my back. I waited a round to do it by which it was already to late for everyone else to stop me.
Basically my opening was:
- Recruit a high priest
- Move acolyte
- build gate
- remove gate (gain spell book +high priest)
- sacrifice high priest
- build gate
In doom phase summon great old one for free (oh yes, did I mention that, Ubbo-Sathla is free to summon in the doom phase you only need a high priest, which you'll get back immediately thanks to hierophants.)
Do a ritual of annihalition. No one does it this early, so it's still cheap and you get an elder sign, another spell book and another high priest.
In the last round I had five gates. At this point naturally everyone turned against me, but it was too late. True, I was lucky with my elder sign draws, but I won with a big enough margin that I still had room for some worse draws.
Edit: The second game we played the player using the Tcho Tcho made much worse use of hierophants and still managed to win just thanks to the Hell Banquet (when a player does a ritual of annihalition he can either give you one doom point or receive one less.)) unique ability and Tablet of the Gods.
Overpowered might be a strong word, but they certainly mess with the game balance and not in a good way.