Mana is sparce in this level, so only create spells when you need to.
These spells are worth considering:
fireball - for puzzle 1
heal - incase Aurax takes critical damage
summon eagle - for puzzle 6
summon centaur - for your army
puzzle 1 - faeries
Walk right into the first room . A timer symbol will appear in the top left of the screen.
You now have a set amount of time to kill as many faeries as possible.
Press escape, enter the options screen, and reduce the game speed to the minimum setting.
Now walk around,
and when you have a clear shot fire 2 fireballs at each single faerie.
You'll use 10 fireballs in all, and gain 5 mana sprites for your trouble if all are dead when the timer runs out.
Therefore mana wise, you'll have made a slight profit.
Increase the game speed back to normal before continuing.
puzzle 2 - greed
Simple enough. At the next stop  there are 3 chests. Only open 2 of them, or you'll have enemy
knight trouble. There is a single mana sprite in each chest.
puzzle 3 - corridor of fire
Only Aurax can operate the lever 
which will shut off these meteor showers, so make him walk through.
He will take some damage, but nothing critical.
If you really want to take less damage,
will better protect him.
totem of pacifism
didn't seem to help, so this is no real puzzle.
puzzle 4 - lawful emplacements
Summon a single centaur
and make him attack the turrets  and [A].
He will take negligible damage,
as the turrets cannot fire at close range.
He'll also collect a summon eagle statue which may prove useful for puzzle 6.
puzzle 5 - judgement
This is the reason we used a centaur.
As he walks into this room ,
judgement will activate.
If you've already created chaos or neutral troops, they will take damage,
but lawful troops like the suggested centaur will be healed back to full strength.
Make the most of this!
Only create lawful troops,
and if they get critically injured during the rest of the level, send them back here to be healed for free.
creating an invincible army
Create a second centaur in this room .
Get one of them to force attack the other (right click the target while pressing 'A')
BUT keep your eye on the victim's health. You do not want it to die.
Stop the attacker after 2 or 3 hits, let the victim get healed by the room's judgement spell,
and then resume the attack.
Eventually your attacking centaur will gain enough 'battle experience'
to upgrade to a chief centaur, and finally to a lord centaur (depicted by a gold breastplate).
A lord centaur will heal other centaurs!
Using the mana sprites gained so far,
create 3 more centaurs and move your powerful self-healing army north, out of the room.
This army is all you will need to defeat all in your path.
If you are prepared to wait,
you can do the same with elves. Use the lord centaur as their tough target
so the process requires less housekeeping
(as the elves won't have enough time to kill the lord between judgement bursts).
puzzle 6 - the chest switch
This puzzle is optional, but the switch 
will open the chest [B] to reward Aurax with 3 more mana sprites.
The trigger is not immediately visible, but is on the other side of the chasm,
on the north-west corner (the opposite corner to where Aurax entered the room).
Create an eagle, and stand it on one of the other corners (so it's range to the other side is shorter than the diagonal distance).
It's line of sight will uncover a ledge on the oposite side of the chasm
which you can now click on to make the eagle fly over.
HOWEVER, after the eagle had flown part of the way (and uncovered the guarding emplacemnt) make it fly back.
The emplacement casts gorgon stare,
which will turn the eagle to stone and make it fall to it's death.
But now you can see the emplacement to attack it, either by wasting mana with 5 fireballs,
or by using any chief or lord elves you earlier created (normal elves can't fire as far).
With the emplacement destroyed, send the eagle back over to land on, and therfore trigger the floor switch.
A cut scene will show the chest [B] in the room to to the left of the chasm, and an unlocking sound will be heard.
It's a nicely thought out puzzle, but the reward is lousy :(
puzzle 7 - guarded mana
The three rooms in the north-east corner of the map all contain a chest holding 2 mana sprites.
But opening any of these chests causes 3 enemy creatures (a combination of knights and faeries) to appear.
It's up to you whether you think the reward is worth it.
Stand your army in the center of the room before Aurax opens each chest to ensure Aurax takes minimal damage.
puzzle 8 - storm giant guard
The army of self-healing centaurs will easily damage the Storm Giant, especially at close range.
Alteratively you can use pestilence and return when his health is low.
If you've opted for the raise dead
spell instead of heal, you can resurrect the giant for your army.
The first key is contained behind the storm giant in his chest.
puzzle 9 - knight causing meteor shower
In the next room to the left  is a knight.
When he spots you he will head north and stand on a trigger
causing the room to fill with a meteor shower.
You don't need to go this way, but if you really want to,
kill the knight from long distance
using your resurrected Storm Giant or elves.
In the top-left corner of the map [E] are three rooms,
each with a circular mosaic on the floor representing chaos (red), neutral (green), and law (blue).
Only the neutral room is active. Stepping over the naked picture of Numinon(?!)
causes disenchant to activate.
Unless you've been using
scythian bow or
this will be ineffective against you.
A bit of a waste of time really, especially since you don't need to go this way.
A centaur guard in the south-west guards the second key [F]
and will be no match for your self-healing centaur army.
opening the door
When Aurax has collected both keys to the door to the central chamber [G]
it will automatically unlock when he approaches it.
A cut secen will show the door, and an unlocking sound will be heard.
Now Aurax must 'use' the door for it to open. Have your army ready...
Your army of self-healing centaurs will make light work of the minotaur. Moogos.
When he is dead, collect the amulet (a diamond) from the chest in the chamber [H], and leave via the portal.