Will I get banned for doing this?

[Tru3thful]

@StickStudios

But it doesn’t grant items such as Final Fractal because in vanilla Terraria, they disappear straight away, and the item doesn’t really have a name, so it gives nothing.

That’s because it’s intended and baked into the game itself, if you will.

First Fractal is one such unobtainable item, and if it chooses to disappear when obtained through any means, then it should. After all, players aren’t meant to have it. Your method of keeping and wielding First Fractal is through use of a modified client, and the Dark Gaming server rules state:

@popstarfreas

Section 5 - Hacking/Exploits

#1 Hacked Clients [or Modified Clients]

All types of modified clients, that deviate gameplay functionally in any way from the original Terraria client; this also includes using 3rd party programs, such as Inventory Editors, to modify your character to possess impossibilities, but texture packs are exempt*.

Therefore, why would the use of a server command be exempt from the game itself?