Kid Icarus is one of Nintendo's oldest franchises, yet one that has been severely underutilized. 'Of Myths and Monsters' was the second entry on the series, released exclusively on the Gameboy, and while, at the time, it was praised for smoothing over some of the first games rough edges, I'd venture to say it hasn't aged very well at all.
The plot is a bit silly and entirely inconsequential to the game itself; basically, Goddess Palutena has a dream about Orcos invading the heavens, so she sends out Pit through a series of training challenges. And, spoiler alert, as soon as you finish the training, Orcos attacks and it's up to Pit to save Palutena. The game is divided in 4 stages, the first three with four sub-stages each. The first three stages would be Pit's training, and and on the fourth sub-stage you are thrust upon an annoying maze-like environment that concludes with a boss fight.
Most levels are relatively linear affairs, either go from left to right or get to the top of the stage in order to beat it. But you'd better not, as spread throughout them are different doors that will take you to stores, healing springs or bonus stages. Currency is earned by killing enemies, and you will need to go out of your way to grind for enemy kills, which spawn infinitely, if you want to buy anything, as everything is plenty expensive. Among the bonus stages are 'survival' type affairs, in which clearing them awards you with one of three weapons. These weapons only work when you have a determinate amount of health on your health bar, but you'll need two levels at least to use the first one of this weapons. Your health gauge is increased by amassing a certain amount of points, and after clearing a level, if you managed to get enough points, Zeus will upgrade your health to a maximum of five.
Honestly, I thought the entire game was a waste of time. You are expected to sit near enemy spawners and kill them ad nauseaum to amass currency and so properly equip Pit for the different stages. However, to say that the game was devoid of any fun would be wrong, as some of the platforming in the latter levels was decidedly enjoyable, and seeing Pit get stronger as you get more life upgrades and weapon upgrades felt pretty satisfying. Once you are fully equipped, it becomes even more enjoyable, as you try to avoid damage in order to keep your upgrades activated.
Bottom-line is, I think Kid Icarus is a victim of age. And while the game starts off very boring, once you've amassed a small fortune and are well on your way upgrading Pit, it becomes relatively enjoyable.
4.5 out of 10