How to make a Multi-Client

Firstly...
Backup your Tibia folder!
usually found in "C:\Program files\Tibia" (assuming 'C' is the drive letter of your primary hard disk or partition you installed Tibia to.)

Get HexEdit or another hex editing program (Hex Workshop 4.23 Avalible at Tools page =), Open Tibia.exe in your hex editor and jump to hex line 9B2F9, you can paste it into the "hex jump" box and just hit return.
It will take you to the 6 hex digits that need to be changed, (8B 48 74).
just highlight them and overwrite them by typing 909090, then save your work, close the hex editor and run the client.

If you did it properly you will have light all the time IF you equip a rune, firesword, brightsword or any other item that gives light colour, (i just leave a uh rune in my ammo slot.)

Same for MC, hex jump to address A9D5C in your hex editor and edit 7E to EB, and save, close the hex editor and run tibia.

If you feel confident enough, do both Light and MC at the same time, then save.