Ok, so every level in Rezrog is procedurally generated, and every level is different... Except for the layout of this dungeon. The only thing that changes is the location of the poison spewing gates that litter the floor. Try to avoid them as much as possible as they will damage your character.

As you enter the dungeon, the door slams behind you, never to open again, the only way out is to get to the other end of this dungeon. In the northeast corner of the room is a weapons table that contains starter weapons for your class:

Magic users get a staff
Rogue gets a pair of daggers
Archer gets a bow
Warrior gets a sword and shield
Paladin gets a two handed sword

The weapon(s) will be automatically equipped if you don't already have a weapon.

A door out leads north.

As you enter the next room of the dungeon, you will see a quite long room, wandering around in the shadows on the other side of the room is something terrible! A larva!

If you have a bow or a staff, if you line up along one of the straight lines, you can engage the creature at range and hurt it before it gets to melee range with you, if not, approach the creature with your weapon, and when you get close, you will enter combat mode. You can move 2-3 spaces (depending on your character) and perform an attack or pass your turn if you are not in range to attack.

The Larva will bite for a small amount of damage, or release a cloud of poison into the air that will occupy a tile until the fight is over. If possible, try not to step into the gas cloud or over any gas vents in the floor to prevent as much damage as possible to your character.

One thing of note, and this pertains mainly to melee characters, is that your position regarding a monster is important. On the little base of the character and the monster is a small arrow that sticks out of one side of the base, on the player, it is green, on monsters it is red. That indicates what way they are looking. If you attack them from where they are looking, they are more prepared to defend against that attack, and you will do slightly less damage. If you have the movement and the space to get around to the side of the monster (or even the back!) and you attack from that position, you will cause more damage to the monster. However, don't give up the ability to attack at all when trying to get extra damage on an attack, as even some damage each turn is better than none at all (and possibly giving the monster free attacks) (thank you Skull for mentioning this in the comments to remind me to add this information)

When you defeat this terrible monster, you will notice a barrel in the corner of the room that will contain a little bit of gold and 5 healing potions. Again, a door leads off to the north.

As you enter the next room, again, it is a large room, with a book on a lecturn right in front of you as you enter, if your character hasn't already obtained this skill before, it will be learned by your character when you interact with the lecturn.

There is a rat at the end of the room, Rats are slightly more dangerous than the Larva from the previous room. The rat first of all moves a little bit faster, but it also has an attack that causes you to bleed each round after it bites you.

Test out your new skill on the creature, if you are running one of the staff users, the skill will deplete some of your mana pool. Otherwise the skill will have a cooldown. Once you pummel the rat to death, again in the corner of the room is a barrel that contains a bit of gold, and a set of 5 mana potions. If you are low on mana, drink a few, if you don't use mana, you can either hand them to one of the characters that does later, or sell them for extra money.

Make sure you are healed up and ready for a big fight before proceeding through the door to the west.

As you enter the room, on your left is another Lecturn with your second skill for your character, on the other side of the room is a wizard looking enemy, and the boss of the dungeon! Prepare for a real fight, as this is where most people fail the first few times and get frustrated.

The Wizard when engaged will be able to summon a skeleton minion to try and engage you. Otherwise, he will try and shoot you from range with his staff. His staff will do around 10 damage per shot, so he can kill your character very quickly! The skeleton on the other hand, will only usually do 1 damage per attack. The key to winning this battle is to kill the wizard and ignore the skeleton.

The warrior has the easiest fight here, as his shield bash skill works very well against the wizard, stopping him from being able to summon the skeleton.

The mage can also get in the wizard's face and use the ice slab to stun the wizard for a turn while you shoot him down.

Anyone else, just do as much damage to the Wizard and he will fall over dead very quickly.

If you win, you have finished all the battles in the dungeon, and will have hit level 2 now and been completely healed and all your mana is restored. You also will have 5 statistic points to spend on your stats.

Another door leads off to the west.

As you enter the next room, you will be walking into a jail, inside the cells will be a townsperson (the Innkeeper if this is the very first time you have defeated the dungeon) as well as any of your characters that have been trapped in the dungeon by being defeated by the wizard. Open the doors and they should disappear and will be waiting for you in the exit room. Before you leave the jail, there is a chest in the corner by the door. It will contain a bit of gold, a legacy gem on the very first victory of this level, and a random piece of chest armor for your character.

If you open your inventory, you can right click on the chest armor to identify it for free and equip it to your character to provide some protection.

As you exit to the west, the corridor turns south to the exit, around the exit will be any people who were trapped in the dungeon and a door leading to a staircase out of the dungeon.

Exit the dungeon, and congratulations, you beat the first level!