Tot's Know-How was unfortunately removed from the game in the October 2nd patch (v208).
The best way to make your potentials Epic is to use Epic Potential Scrolls. They are available … (more)from Elite Bosses and various coin shops around the game, as well as Auction House (if you're in non-Reboot).
To get better potentials, you use items called "cubes". There are various grades of them. Cubes reroll the potential on your equipment, with some chance of ranking it up.
The weakest ones are Occults, which are readily available from Sudden Missions, Elite Bosses, Harvesting, Monster Collection, and most bosses. Occult cubes can rank your equipment's potential up to Epic, but at a low rate.
Better ones are Master Craftsmans' and Meister's cubes. They are available from the same sources as Occults, but more rarely. They can rank up to Unique (Master Craftsman) or Legendary (Meister).
The best cubes are the ones in the cash shop: Red and Black. They can both get to Legendary rank. The difference is that Black Cubes let you choose between the potential your item already had, and the new potential the cube rolled. All other cubes change your item's potential irreversibly.
For pets, outside of Cash Shop, the pickings are slim:
- There is supposedly a new quest at level 33 that gives the 7-day Puffram, in place of Tot's Know-How.
- The boss Hilla has a chance to drop a box that may contain the 90-day pet Blackheart (that can be revived with Water of Life). Normal Hilla (accessible, and generally beatable, at level 120) has a low chance to drop this box, but can be fought daily. Hard Hilla (accessible at 170 but not easy to beat even above 200) almost always drops the box, but can only be defeated once a week.
- If you are not in Reboot, the new pets from Wisp's Wonderberry are tradable, and people have been selling them in the Auction House. (less)
