There's a couple threads about awesome tricks with flesh golems, but it seems that most strategies build around FGs have a few critical flaws:
- By the time you have a figure with channeling 3 and can make a flesh golem, you're usually in late game, when the relative impact of one powerful figure is usually much smaller.
- Level 3 spells are an extremely valuable resource; most of the time you're better off spending your promotions of channeling 3 figures on spells that can be used repeatedly, rather than Graft Flesh.
- Producing figures to add to the flesh golem is usually a bad investment compared with just using those figures directly.
- Get a figure with channeling 3 much earlier than usual.
- Put the Body 3 promotion on a figure who won't be around long, or whose promotions can be reset.
- Add useful promotions to the flesh golem without spending hammers to get them.
- Gibbon and Corlindale.
I often beeline Trade after getting the needed worker techs, since being the first civ with Trade allows you to take a big leap in techs. Deception is just a quick jump from there, even if you include the price of Way of the Wicked, and it opens up Nox Noctis (easily one of the top 5 wonders in the game IMO).
Any Flesh Golem Gibbon makes will be an illusion, of course, but as long as you steer that unit well clear of any Empyrian civs, that's not necessarily a bad thing. A powerful illusionary golem can serve as the leading point of the spear to weaken a strong defender, and leave the kill (and the XP boon) to another figure.
Fanaticism isn't quite as short a path, but if you're going for Aristocracy, it's only one more step, particularly given that you need Priesthood to solve the third Flesh Golem problem anyway. (The Mercurian Gate is another of my favorite wonders, too.)
The next earliest figures with channeling 3 are Govannon and Hemah, who can be reached at Arcane Lore. But that's a longer path still, and it's an otherwise fairly useless tech. Govannon's promotions should all be level 1 spheres, anyway.
- Gibbon and Corlindale, part 2. Not only are those two figures the earliest archmages you can get in the game, but they also both have a powerful spell that kills them. Gibbon also restricts you to Council of Esus while you have him, which is good for diplomacy but not much else, so it's nice to use him and get rid of him.
Playing with the knowledge that you're going to eventually kill your archmage also allows you to invest promotions in the other level 3 spells that feel like a risk or a waste. The three I'm thinking of are Trust, Resurrect, and Domination. Obviously, if you have both Gibbon and Corlindale, then giving Gibbon Ressurrect is a no-brainer. Make a couple flesh golems, kill Corlindale, resurrect Corlindale with Gibbon, kill Gibbon, and have the new Corlindale proceed to different spheres of spells while you keep your two FGs.
Again, Hemah and Govannon offer other, somewhat less attractive options. Neither of them can die in an especially useful way, but the other criteria fit. If you want to change religions away from OO, then you can give Hemah Body 3 along with other one-off spells before moving on. And the same trick I outline above with Gibbon and Corlindale can be done with Gibbon (or Hemah) and Govannon.
- Tigers and Mutation. (And, much later, Krakens and Mutation.) Building warriors and scouts to bag promotions is wasteful. But if you leave some priests of leaves and one mage with chaos 2 alone with a flesh golem for 20 turns or so, you will probably end up with a Flesh Golem that has all the really useful mutations (the resists, blitz, light, strong, cannibalize, heroic strength/defense). If you manage to get a priest to combat 5, then your FG gets empower 5, too.
You will probably want to throw one or two other figures in the FG at some point. (Mobility 2 is really nice if you didn't give the summoner Extension 2, and I'm partial to the commando/water walk combo... I like fast figures.) But just the mutation promotions above makes for a pretty fearsome package, and it comes without a big hammer cost.