Ok, I would really like your oppinions on this topic, because apart from some exceptions (especially the Zynaryx Plate), I found most of the Custom Items by the two Rapax smiths to be not really worth it.

Here's what I think about them:


BEASTSLAYER AXE
This is indeed the best one-handed axe there is, and vs. Beasts it's amazing of course. However, Axes in general are not very great, and even if you go for them, you are probably aming to wield the Blades of Aesir one day, which is (of course) two-handed. Which means your Shield skill or Dual Weapons skill will be worthless. Another issue is the Giant Picus Egg you need. Once you have it, the Axe is likely outclassed by other weapons. Overall not really worth it.

EBON STAFF:
There is a big performance slope for staffs (if you're not a Ninja or Monk). In the beginning there is basically only the Quarter Staff, and then at some point you can get the Staff of Doom in the Mountain Wilderness. For the time in between this one is indeed a very good Staff. However, it can only be used by your spell casting classes, and if you really want to you can get the Staff of Doom fairly soon. Maybe not quite as soon as you can clear Marten's Bluff for the Ebon Gem, but soon enough for the Ebon Staff to be outclassed rather fast. So, this on IS good, but its competition is tough.

ZYNARYX PLATE:
If you have a Fearie (no Monk or Ninja) in your party (likely some spell caster), this one is the best armor for a very very long time, maybe even for the whole game. You also get it very early, which makes it maybe the single best custom item out there. And also the only one I'm totally convinced it's worth the effort.

STEELHIDE BREASTPLATE:
You can get this one pretty fast, and it is a good armor for your Ranger, Bard or Gadgeteer. However, there is also the Chain Mail +1 (U), which has the same AC bonus, also has the 10% water resistance, has additional 10% fire resistance, and it costs less. If you happen to not find a Chain Mail +1, the Steelhide Breastplate. is actually very good, but only for a while (you can buy the Chain Mail +1 from Ferro).

FEATHERWEIGHT ARMOR:
This one is very likely the last custom item you can get from Antone. And then... well, I'm not sure at all whether it's worth it. It has +10 AC... and nothing else. Its only feature is that it has a weight of only 5.0 (for comparison, the Steelhide Breastplate weighs 26, the Chain Mail +1 weighs 30). Now, encumbrance aside, there is this rumor that your total load carried affects the frequency of Lightning Strike of the Samurai, which would make the Featherweight Armor the ideal armor choice for him. But of course this is by no means confirmed. Also, if I find a Hi-Kane-Do one day (AC +12, 30% Fire resistance, weight 35) - is this now better or what? I have actually no idea about how important this lightweight feature is. Maybe it's good enough?

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MIRROR ARMOR:
Now, this one is totally useless. It's probably not very hard to get the components (if you can find a random Locket of Reflection), but the very same Ferro you can get this from also has the Golden Breastplate, which is easily way better (higher AC, better resistances, less weight). Even the Ebony Plate is not really worse, so there is no reason whatsoever to go for the Mirror Armor. Ok, it's feature to reflect damage to the attacker is neat, but not really much more (this damage won't really matter, and you can always cast Razor Cloak if you want the effect).

IVORY BLADE:
Ok, the Ivory Blade is interesting. It is certainly a very good sword, but it has a very serious direct competitor, which is Fang. You quite likely have Fang already until you are able to get the Ivory Blade. Fang deals 10-24 damage (mean: 17) with +2 To Hit and +2 To Initiative, and it gives +10 STR. The Ivory Blade deals 7-31 damage (mean: 19) with +4 To Hit and +5 To Initiative, and it has a +1 AC bonus and can cast Haste at PL 3. However, the Ivory Blade only has a 1% K.O. bonus, while Fang has a Kill bonus of 10% (!), which is huge - only the Muramasa Blade has more (15%). So in terms of mere combat performance, the Ivory Blade is better, while Fang has the better bonus effects (and the +10 STR of course also adds +20% to the damage range, i.e. something like 12-29, mean 20). What makes either one or the other more interesting are the class restrictions: Rogues, Bards, and Gadgeteers can wield Fang, but not the Ivory Blade, while the Ranger can wield the Ivory Blade, but not Fang. But for my dual wielding fighter, I have no idea which sword to prefer. Probably Fang?

VAMPIRE CHAIN:
It's quite funny. You collect all those components to finally get the great Vampire Chain, only to realize that the same vendor also sells The Mauler, which not only looks better (higher damage, higher Mace bonus), but also costs 7,000 instead of 100,000 (!). And you don't need any special ingredients. So, what is it about the Vampire Chain? It has a bit higher To Hit (+3 instead of +2 of the Mauler) and it has a Inititive bonus (+3, instead of -1). It also has this neat (but not very crucial) Lifesteal effect, which replenishes your HP if you damage an opponent. Then it has 100% Drain Stamina as bonus effect, instead of 1% Kill and 10% K.O. of The Mauler (I have no idea how good this is). But the two big things are: a) The Vampire Chain has extended range, and b) It can be used by Faeries, which makes it a super-great weapon for your Faerie Bishop hiding in the back ranks. But for the standard front-line Mace-wielding Lord, I would still prefer The Mauler I think.

I actually like to give it to my Human (or Elven) Bishop when I manage to obtain this. This weapon (and other whips as well) has a couple properties that make it ideal for this character:
1. It is extended range. Hence, my Bishop can attack from the back row with it.
2. It is one handed, so I can still give my Bishop that Thieves' Buckler for the Speed (and Initiative) bonus, or the Lithe Buckler for the Stealth bonus (to make enemies less likely to target her).

Drain Stamina tends to me more useful in longer battles; if you can drain an enemy's Stamina to 0, it will fall unconscious and not stay awake long. KO, on the other hand, causes immediate unconsciousness, but once the enemy wakes up (assuming your double damage physical attacks don't kill the enemy first), the enemy stays awake unless knocked out again.

Incidentally, whips (including Bullwhip, Chain, and Cat O'Nine Tails) have a couple unique disadvantages:
1. They get reduced Strength bonus (and penalty!). This isn't a problem for a Bishop.
2. They do not do double damage to sleeping or other disabled targets.

2nd best... the best is
Plague Axe = http://www.zimlab.com/wizardry/recovered/flamestryke/wizardry8/itemsw8/weaponwiz8/axes-plague.html
but this one will go on my dragon Valkryie until that area is open.

p.s. the wilderness area has eggs and you can get there around level 14 without major stress.

You summed that up nicely. Zynaryx can be best in slot in specific scenarios (only until you become a Rapax Initiate if you play a solo). Ivory & Steelhide can be used till the end but aren't best in slot. Vampires Chain is nice and although it is not necessarily best overall it is among the best weapons for a Bishop. In fact I switched around a lot and mostly used Diamond Eyes and Vampire in the end. Depended on the enemy in question mostly yet the health gain is also nice albeit not even mentioned in the description. It really is the Vampires Chain after all. Would be even better if the weapon was good enough to use on a fighter type char with a bigger health pool... alas it can't compete with the best swords.