NeonQuasar

Ok guys, case closed. Turns out i was indeed missing a quest. Thanks to everyone for the help!

Yes, here it is. With what i've done, i believe there should be a cube 3 there. And the NPC does in fact say that he can't upgrade my cube more. The last cube upgrade was done in Tigraki island, since i forgot to do that when i was there and the only thing he did was unlock the third row of my Cube 2. It sounds like i did something wrong with the order that i upgraded, but i don't know if it can be fixed or i have to keep playing with these cubes. And probably one more? (Since i haven't done the Expert Crafting quest yet).

I'm Selius, (Asmodian assassin) and after upgrading my cube to the max and doing the quests Unexpected reward and Materials for 100 slot cube, my inventory has only 3 cubes (Default Cube, Cube 1 and Cube 2). I did upgrade my cube at Tigraki Island, in Ishalgen and Pandaemonium, i probably didn't do it in the correct order? As a result, i probably have to play with less cubes now. Is there a way to fix it, or do i have to play like this?