If you have spell leech on a unit with enough initiative, you can build up a lot of mana in a single battle.  Air elementals, fell dragons and a few others love casting 1 turn spells...

Stinking Mud can help here, and so can defensive abilities (for when things go wrong.  I do not know how much mana you can suck out of a dragon, but it's over 9000. Mind you, that would be really boring.

Here is a midgame strategy that combines the charge/impulsive abilities which the AI cannot defend itself agaist (on challenging at least).  In my opinion, the reason why it's overpowered is because the strategy can be executed too early in the game (would be better if it wasn't viable until end game).

1)  Level your fortress up to level 3 and give it the first strike improvement so all units trained in that city go first in combat.

2)  Start spamming horse cavalry with the charge ability.  Give them a weapon with a high attack (I like to start with broadswords because I can quickly upgrade them to Athican Longswords for very little cost).  Your stack should consist of only horse cavalry so that you can get 4 moves on the map and reach the enemy cities quicker.  When possible, I give them light plate as well, but the first couple units may not have light plate yet.  Just keep spamming units with better and better equipment as the techs become available.

All of your units will always go first in battle, and will have 7 moves on their first turn, meaning they can charge most of the enemy troops/heroes before the enemy even gets their first turn.  They deal out extremely high damage on their charge (usually between 40 and 60 damage with an athican longsword).  Juggernauts will be cut down before they can ever raise their axe, most mages are killed before they can ever cast a spell.  You will be able to decimate most of the enemy's army before they even move.  Battles are over before they even start.

The death worship ability gives the ability to transform any mana node to a death node. Death + Air gives a spell called contagion which does 3+1 per death shard poison damage over 10 turns. This is boosted by +% to spell damage.

Against AI non resistant to poison armies (ie pretty much everything I saw) mid to late game the combination is unstoppable. With six death shards my champion was doing 30 damage per round for 10 rounds from this spell (but battles never lasted ten rounds). Thats not including whatever damage my army could do. Yes you do need to win a spell resistance check but of course I took the ability that boosts spell mastery every level, added the warlock ability and picked every mage boosting perk I could.

Tuidjy: I can't create the leader you describe the OP due to not having enough points ( need one more ) . did they reduce faction points for custom leaders?

I just recreated him.

Did you choose clumsy before you tried to take three talents?  Clumsy is a weakness, and you have to take it before you take wealthy.

Beastlord: 0

Air: 2

Water: 2

Brilliant: 1

Attuned: 1

Wealthy: 1

Clumsy: -1

Sword: 0

--------

Total: 6

This was in Vanilla 1.02 

Do you have mods enabled?  Some of them, like the awesome Stormworld, raise the price of beastlord.

Tried the henchman route, twice.   Fun and nigh unstoppable.  I played around with the types so I had a type of each element since I didn't want to bother with spellbooks.  Just nasty.   Fun though, best part was that you got to see every quest MANY times and experience all the loot.

Some random observations:

Its annoying when some other civs trade gold for twice as much as normal - i.e. 50 of their gold has 100 worth.  It changes, and I'm not sure why some civs do it at some time and then not on others.

The "Maul" ability is by far the best.  I would rather have the berserker sword/axe than any other weapon.  Even with heartseaker and the other one, its one attack at 30-50ish depending on armor.  With Maul and some good accuracy, its 10-20 multiple times, frequently outdamaging the rest.  Plus, while cool - 2h weapons are nice and all, but lack of a shield is tough.  Especially the ones with special abilities.   When I get that "find the garrotte quest" I chortle a bit, usually out loud.  Its a bit sad.

The quest making mod may be real useful for this approach, the quests become old kind of quick.

With the constant fighting, mana is a bit of an overused resource.  Having "spell leach" is nice for the haunter battles.

There is a champion that autocasts mass curse at the start of every battle.  AWESOME.

I tried one with betrayers and the mod that makes quest maps always available.  I never really saved up enough for the 500 to turn the oppponents cities...I always wanted more maps and was scratching for cash.  Not sure why.   Possibly because I also picked up "Adventurer" as a job instead of beastlord and picked up a bunch of champions - meaning i had an ok amount of upkeep.

Was a bunch of fun

FYI - just tested.   GUILE (double influence) does NOT stack with Heroic.  i.e. you don't get 100 per quest, just 50.

I tried a Guile, Heroic, Master Scout, vulnerable to magic Trog civ with a diplomat  Sov to buy their units away.   Just tested it out, bailed when it didn't overpoweringly give double influence

It depends on how much gold they have; if they're low (I think it kicks in somewhere <200 offhand) they start valuing what they have left at double. You can actually pull some cheesy stuff by trading them just enough gold to get them to the point that they value it at 1x (get something decent for your gold, of course, don't just give it away..) - and then getting them to trade every penny they have back to you, all at once at the lower rate.

You can combine this well with trading other resources (metal, crystal, horses) - AIs will pay well for those resources if they're short on them, somewhere around <50, but place no value on them if they have 50+. Sometimes you can get the AI to give you just enough of a resource to put him under 50, then trade him back a hundred at a decent price.

So say you have excess metal and you want gold; an AI is down to ~150 gold (doubling its value to the AI) and 55 metal (meaning the AI places no value on your metal) - you can trade the AI 50 or so gold for 6+ metal, now the AI is valuing its 200 gold at 1 point per and paying well for your metal stockpile since his metal reserves have dipped below 50, so you trade him sufficient metal to get every gold he has.

Suffice to say it's a strange system full of loopholes; the only reason I don't mind exploiting them is because the AI is so unreasonably determined to cheat you on every trade and treaty, even when said trade/treaty would benefit the AI more than you anyway. I mean, for example, if the AI is short enough on gold to be valuing his gold at 2x, you'd think he'd pay 2x for your gold as well, no chance of that. If he has so much extra metal he places no value on your metal, you'd think he'd be willing to trade you some of his at a discount, good luck with that. And if an AI's economy is so far ahead of you that the tech treaty will give him 4x the benefit that it does you, why does he demand several hundred gold for it too? Diplomacy is neither fair nor logical, you have to take what little advantages the flaws in the AI will give you.

I trialled Adventurer with Betrayer and Master Scout a few days back, stopped it when I had explored most of the map, had about a dozen heroes and the AI had next to none. As long as you find a couple of heroes early it snowballs, you can cover so much ground to find heroes, and naturally you prioritise the techs to hire them.

I think the denial of heroes to other civs is more powerful that the benefit you get from them, which diminishes with higher numbers.

I started a game with altar and Relias, to test this tactic. It took me some more turns to get the henchmen, but once I got them...OMG! this should be forbidden.

Quest Maps + Stacked Shieldwall + High XP gain (potential, traineer) + Lightning hammer it is simply too much.

But wait, you still have to add, when leveling, other traits like tactician or leadership...

There is no fix for this.

Let's say, for example, that Shieldwalls did not stack, you still get a fast leveling units with scaling damage. And armor can be pretty improved in fortress...

Nerfing the lightning hammer is not good idea. So I gues the only thing should be making something to Quest maps, and that would mean the rage of many people...

Would making none of the perks that effect the whole army (trainer, shieldwall, leadership, etc) stack fix this and other issues?

of course I'm running Stormworld, why wouldn't I?

too bad, I wanted to try your combo. I also didn't realize spellschools cost 2 instead of 1. I think I've created a similarly abusive combo yesterday though, still based on the OPness of the quest loop:

RACE: Men blood, betrayers, heroic, wanderlust, rebels, skeptical ( from additional faction traits mod )

LEADER: adventurer, earth, water, scholarly, sword

I wanted betrayers because I hate meeting opposite alignment heroes I can't recruit. I also enjoy adventurer, and they go well together like heroic and wanderlust

One issue with quest maps is how little traveling you need to go through to complete a quest. This is fine for the initial quests but once you have done a few quests it's reasonable for the positions to be randomized over larger and larger areas.

Custom sov, full melee build with resurrection and ritual of blood. solo the game with 4 digit HP

It seems that might help, untill you see that, instead of travelling far, you just buy more quest maps untill you get a "quest route". I found that the "stone ring quest" seemed to be broken as it did not trigger, so I had 3 or 4 "stone ring quest" around my dominions. What did I do? Just buy another quest map.

Well, I don't mind. I'm against quest maps, and more now, that I tried this "trick"/"exploit"/"OP tactics" or however you want to call it. I will not use quest maps again.

It is personal taste: linking XP to money is not good for immersion. It is like you could buy "Experience books" for 50 gildar, but instead of 15 or 30 XP points, they gave 300 (or more), and could be read many times (one per member or the army).

Yes, it would take some play testing to get this right.

The idea would be to balance the amount of gold you would need to have invested to pepper the region with quests with game progress.  Anyways, you are right, if there is not enough room on the map to make the distance mechanism work right the cost of the maps would also need to increase.

Maybe have multiple quest scrolls for easy  -> deadly?

Takes a bit of the gamble out of it, but at least you can't rock a deadly quest for a mere 50 gold anymore.

How were you able to do this?  Every time I try to make terrain impassible with the raise land spell it says I can't make it any larger plus the spell description says I can't make a hill into a mountain.

Have you tried using curgen's volcano? (I have not, but I am in a situation where I think I want to...)

I've only used it on other cities but I suppose that would work.  I know when you use it on other cities it makes everyone else declare war on you in a few turns but I'm not sure if they declare war on you if you use it in the middle of no where.

Three dragons at the front of the army.  Now that's overkill.

The strongest Set-up I've found would have to be the one man army theme          NOTE: {BETA} Legendary heroes skills

Race: Wraiths blood, Binding, Death worship, Lucky, Master scouts    - M-scouts not needed but i like the movement

Leader: Wraith blood, Hunter, Death apprentice, Brilliant, Hardy, Discipline, Veteran, Might, Cruel

At game start i make my leader an Assassin, the Assassin has the most potential and the best stats for late game especially if built with arcane armour as it give stats per level

The other thing that makes this build so powerful is that even tho your a fighter you have extreamly powerful magic thanks to "Death Worship" and you always have an army thanks to "Binding". this allows the player to ignore War research completely as your hero should be able to easily dispatch entire armies provided they are not all Dragons or Obsidian golums

the thing i like the best about this build is that while you only start with Death magic you use those useless heroes that only sit in your towns or suicide on enemies by killing them and taking one of their Magic's goes very well with the One man army theme

Same here Dark Wizards are OP

I actually prefer fire over air, and then boost crit chance.

at level 15, with a bit of luck I have around 30 - 40 crit chance (depending on gear), and flame wave is just... brutal.

often get an entire strong army completely cleared with one shot.  The giant demon army at the end of the LH scenario?

took out all the demons except the 5 that were fire immune in two turns... that's NOT using the "god powers", which actually did LESS damage.

you often can get 150 damge per crit hit, sometimes over 200 or higher.

my flame dart took out Vestrar in ... one hit.  first round.  This is all at level 15 mind you.

blizzard is great, but it takes too long to cast, frankly.

aside from that... yeah, beastlord... total snowball effect.  to fix that, all that needs to be done is to make your tamed beasts COST something per turn to maintain; preferably food (takes a small fraction of your faction food stores to maintain).  Each monster you tame would require 1 food (like a basic farm) to maintain.  Watch your food surpluses disappear if you tame too many beasts.