What server are you playing in, what map are you in, and how new is your account?
Reboot has trading disabled, I'm fairly certain you can only access Auction House in towns, and new accounts are restricted from purchasing or selling items in the auction house for 7 days.
It has no control over your character or the game itself, and should be theoretically fine.
But I cannot confirm the game won't detect it as a third-party program. I doubt it would, plenty of players run other programs besides Maplestory, but I cannot confirm that it won't.
The best I can do for you is warn you of the potential risk.
You should still be able to access the Crimson Balrog by traveling to Orbis, going to the Ludibrium dock, and selecting the option "Ask about events related to Crimson Balrog"
There are outfits such as the Bloody Leo:
The Red Avenger:
Possibly the Blood Fitted Mail when combined with certain shoes, such as Dark Katina shoes:
Kaiser Brave Mail:
The Blaster (Female) outfit:
Or Havoc's Uniform:
However, not all of these items may be available, and you cannot anvil an Overall equip onto a top/bottom equip (which may prevent you from using Fafnir gear).
