Okay, so you want the sword.

First of all, you need all 3 magic types. You only need to be able to cast them. Go through the game and just make sure you get at least 3 level of Gravity, Fire and Lightning Crystal.

When you go to the end, you need to get up to the pillars beneath the crystals that kill you. You can either climb up yourself, or go through the cracks in the walls to get to two of them, and then from one you can jump to the third.

The one above where you enter needs to have Gravity imbued into the hole at the top, then Fire in the middle, Lightning at the bottom.

The one on the left side when you enter must have Lightning in all three holes, I don't know if it matters but I did it in clockwise and didn't die.

The one on the right side needs Fire and then two Gravity imbues, but this must be done counter-clockwise. From inside the room looking out at the pillar, with the sword pedestal at your back, enter Fire into the left-hand-side hole first, then go to the right hand side and add Gravity, then to the 'back' of the pillar and add Gravity to that hole as well. If done in the wrong order, it will kill you.

Each pillar you infuse with magic should play a sound effect to indicate you've done it correctly, and when all three are done, you can go and grab the sword.

This will cause a bit of magical instability, so my recommendation is you put that sword on your back and run like hell back to the portal you entered through unless you like magical spaghettification.

Congrats, you have the sword now, and can buy Tier 4 items in the shop, enjoy.