Walkthroughs for custom maps.

That is, it can definitely be done, but it may take weeks/months.

Each hero in the game has 255 built-in skill trees; when creating a map, one of them is selected, which means that the appearance of a skill (including a primary one) is not random. Either there is a tree with 8 spells out of 14, or there isn't. If it exists, it is not that difficult to obtain it.