I've been impressed that people often underestimate this powerful item so I've decided to share my knowledge and experience with it.
First of all, some basic stuff and numbers:
Fever fetish is supposed to disease its wielder and to bring 1 fire gem per turn. It is well known that it works poorly on undead and demons (it was way too powerful in times of Dominions: PPP when it could be used on undead) and brings gems rarely. I used fetishes a lot in all games I had access to them and I noticed that fetish brings gems more often when its wielder has less HP than the base and so I decided to disease commanders a turn before I planned to wear fetish on them. Yes, it was even more time consuming but it made fetishes more effective.
The exact numbers were given by Ich recently. So fetish has a
- 25% chance to bring a gem when its wielder has base HP
- 50% chance when wielder has 1 HP less
- 75% chance with 2 HP less
- 100% with 3 or more HP less.
So, it is probably most effective to wear fetishes when commander has 2HP less because 75% is a good chance and 3HP less makes the life of a low-HP wielder really short. It's quite simple to do - just equip a healthy commander with a fetish, then remove it (commander stays diseased) and then equip it again in 2 turns.
Also, these maths explain why fetish works poorly on undead, demons and commanders with regeneration – they all just never lose HP to disease. OTOH, if you give a regeneration item to a fetish wielder when he has 3 or less HP, it will bring gems forever.
But yes, all this requires a tremendous amount of micromanagement. Planning how many fetishes you'll have two turns later and checking each wielder's HP so that he doesn't die can really be a pain (for everyone who is not micro fan like me). Is it really worth the gain? Yes, it is because this micro allows you to always get (roughly) 1 fire gem per turn with this cheap item. If you want to win this can be invaluable.
It is often said that clam is more effective than fetish because fetish brings (nearly) useless gems, requires a lot of micro and money to recruit disposable commanders. All this is true in some aspects but even if we say that 2 fire gems are equal to one pearl…
- 2 fetishes (with hammers) cost 6 fire and 6 nature gems (12 total). They pay for themselves very quickly in terms of fire gems but require more nature.
- 1 clam (with hammer) costs 11 water and 3 nature gems (14 total) and clams don't pay for themselves at all because they give gems of type they don't require to make (of course you may alchemize but then the numbers will be different).
So minuses of fetish are more mages (and hammers) to produce, more nature gems (which may be quite important) and gold for disposable wielders but in pure numbers it looks more effective. I think that you see now that they may be really effective even if 2 fire gems are considered equal to 1 pearl which is not true because there're other good ways to spend fire gems in most cases.
Now let's talk about those wielders mentioned above that you have to recruit if you go fetishing. It is obvious that the more HP fetish wielder has the better so if you have access to high-HP commanders, they are ideal targets for fetishes because they will last long and bring a lot of gems for the price (and require a lot less micro). But if you don't have high-HP commanders, the most effective (among indies) wielders in terms of gold spent/gems brought are barbarian chief and scout.
Can these fetish-wielding indies do anything else except just sitting in your big castle and slowly dying from disease and bringing gems? Yes, they can
. If you want to diversify into blood which, IMO, any nation without native access to blood should do, you will anyway need to recruit independent commanders/scouts for hunting. Why not equipping them with fetishes? Being diseased doesn't affect their blood hunting potential at all and it is a good idea to give a fetish to each hunter and then just replace him when he dies.
Also, if you have access to good healers or commanders with recuperation it may be a good idea to equip just anyone (including researchers) with fetishes and when they have 1-2HP remove them and start healing (remember that you may always wear a regeneration item on a commander with 1HP and he will not die until you heal him)
Also, if you have access to commanders with second shape (Machakan Black sorcerers and sorceresses are the most obvious examples) it is worth knowing that they may never die from disease. When they lose their last HP they shapeshift and come with full health the next turn. And they even may cure some afflictions. So it might be a good idea to wear fetishes on those you don't plan to use as battle mages.
Also, there's one trick I discovered recently that made me write all this. Do you remember what I said somewhere above? Undead are poor wielders not because they're undead but because they never lose HP and it is really
important. Now let's imagine that we may have undead commanders with 3HP less than the base… Yes, it means that these undead will bring you gems forever without dying and for no upkeep at all. Sounds sweet, doesn't it? If you go for reanimating your commanders with "Posion Cloud/Life after Death" trick (no matter why you may want it) your reanimated soulless will nearly always have less HP than base 15 due to a minor bug in Dominions engine (which noone is going to fix, AFAIK). The bug is that even if unit's second shape has poison resistance it will receive all poison damage its first form accumulated (I mean green line) so the soulless receive the remains of accumulated poison damage even though they have PR. (The same applies to Machakan spiders, btw) Soulless never heal so they will have less HP after the battle and if any lacks 3 or more HP you may easily wear fetish on it.
All that being said, let's make some conclusions.
You should always think of going for fetishes when you…
- have access to them (you're surprised, I know
- are not afraid of all that micro
- plan to diversify into blood
- have access to good healers or commanders with high HP/recuperation/second shape
- have access to "Posion Cloud/Life after Death" trick
…and fetishes will greatly pay for themselves, believe me…
p.s. One minor advice on micro with fetishes: rename the commanders that you'll have to remove fetishes from the next turn or two for easier access to them later. It is often hard to remember who has many HP and who is going to die shortly. Renaming really helps here.