Some good things to have are:
Lightsaber Blazer
Katana of Miffed Barbarians
Laser Sandwich
Token Gun
Wind Magic
Fire Magic

But do NOT EVER use Kamikaze Magic in your run! You need to save your lives for later when you fight Abarghus.

When you hop in the tower piledrive your opponents and cut them. Use the gun against monkeys. DLC is good for the Tripwire bomb in cas you find areas with lots of white spikes, you can blow them up to stay safe. Or just get Spikeaway, It's quite useful in the long run!
It's OK if you jump over enemies but to stay more safe keep raging. While you're raging you don't have to use the gun against monkeys. Just hack and slash!

The Abyss of nature is a difficult area because it mostly has more traps than monsters. Watch out for the spike balls and spikes. If a room with a bunch of red spikes generates you'll need to have some SERIOUS jumping skill to get across. Also, shoot spike ninjas and monkeys, unless, of course, you're raging.

Here's where things begin to pick up. There will be WAY more traps and few enemies, but be more cautious about electric guys, wizards, and spike ninjas. Oh, and watch out for ground bombers, too.
You'll be jumping a lot, but SAVE YOUR MAGIC. SAVE IT FOR ABARGHUS. It is important that you deal the most damage possible to him with your magic.

Alright some you've made it to the ground floor? Awesome! Now you must fight the One Armed Ninja. What's special is that you can only damage him by Melee, and when he's flashing. The first five times piledrive him so that you don't take damage but he does. Piledriving gives him 3 damage. The last time he flashes you can either attack him normally or piledrive again. Either way, he'll die and give you a life (pickup). Then Abarghus will spawn. This is his attack pattern:

• Roars, then opens his chest and spawns a few bombs and a random enemy.
  
• What you do is kill the enemy and stand in his chest. I read in another guide that the bombs rarely return to their spawnplace.
  
• Roars, then slams his fist into the ground, leaving a blob behind.
  
• What you do is randomly run around when he roars and when he slams his fist in the ground stand on the blob.
  
• Sticks out a tendril and pukes a lake of acid.
  
• This is the only part of the pattern to attack him, so shoot him with projectiles twice and then use magic to deal 5 damage to him.

Repeat until he is dead, and your face should look like this:
Now you can burn the One Armed ninja to descend to the truly infinite basement or exit the tower and recieve the true ending and find out the secret connection between the onearmedninja and the crimson ninja.