To multiclient is to, through one of a few means, use multiple Tibia accounts at the same time. This used to be prohibited but is no longer against the Tibia Rules. Note that the use of modified clients is still a rule violation. It is also known as MC. It is done by either using a program that lets you have more than one Tibia client open at the same time, using a modified Tibia client that allows for multiple clients to be open, using multiple computers, or multiple browser instances running the Tibia Flash Client.