Macchiato Monsters is another descendant of the Black Hack system. Unlike some of its peers though I feel it offers greater freedom with less complicated rules.
The basic mechanics are 5th edition D&D, a d20 roll under your statistics with advantage or disadvantage being handle by rolling two dice and taking the higher or the lower value.
Risk dice are pretty much from Black Hack making low rolls bad and stepping down the die and high rolls lucky. This means introducing a personal frustration of mine where the reading of the dice is different depending on the type of roll you are making.
The remainder of the rules are all some of the simplest and flexible in this family or rulesets that I've seen.
Characters have levels but essentially each level up allows you to use the same rules as character generation to expand the character.
Spells are particularly satisfying because they don't come from a spell list. You do have to pitch your spell to the GM and the GM is responsible for setting the numbers on it, which is a bit disappointing. The guidelines for spell design could be stronger to allow players to take responsible for spells themselves. A simple risk-reward element would probably have been sufficient.
The spell rules are elegant as well each spell has a hit point cost which can be paid for by using component risk dice, you then try to beat a stat in a normal check. Succeed and the spell's effect happens, if you fail you then have the choice to go to a Chaos risk die and see if you can get a favourable result or not.
Combat sensibly keeps to the Black Hack rule of only players rolling the dice but damage is quite variable. It is something I would need to play to see how I feel about it in practice.
Overall I think this rules set was one of the more exciting attempts to blend the freedom of early fantasy gaming with modern game design.