Multiboxing on Lineage 2 is a way for players to open multiple game clients simultaneously so they can play multiple accounts/characters per PC.
Below are the limits for client usage for Lineage 2 per PC.
L2 Aden and Classic: 10
L2 Live: 3
Note: Aden and Classic limits are shared
https://support.lineage2.com/hc/en-us/articles/360047233832-Lineage-II-Multibox-Limit