So there was a lot of question like : "How many accounts i can log in ?" "How i can get another BOX ?"
So theres an answer
To log in with second account(or third;or more acc) you need to buy Premium Account or PA. For each box you need PA. It can be bought in game. In every town there is an NPC called Nostalgia.
There are PA for 7 days and PA for 30days(1 month) . 7days PA costs 30COL and 1 month PA costs 100COL.
You can buy COL in your account at the main site l2classic.club . 1 euro = 10COL. Or you can buy COL in game from trader(common in Giran Harbor) 1COL = 150-200k.
So 7 days PA - 4,5kk(1col=150k) and 1 month PA - 15kk(1col=150k). But also you can buy cols for lower price(using offline trade - wich is free in Giran Harbor) and you will get cheaper price for PA in adenas
Also the information about PA is in this post :
I will believe that this post will help someone !
Good luck in game !