FromSoftware employs a server-side check that parses local save files for discrepancies whenever a player connects to the game's servers. Unlike a VAC ban, a does not prevent play but relegates the user to a "cheater server," making it impossible to match with the general player base. Common triggers for these restrictions include:
If you're a PC player looking for a reliable save editor for Dark Souls 2 SOTFS, I highly recommend this tool. However, be sure to use it at your own risk and always make a backup of your save files before modifying them.
Open your save editor and select the backup or the original .sl2 file.