I absolutely would. Some monsters have ferocity equal to the # of PCs. Very few have 4 ferocity. Most have 2-3. It seems fairly standard. If you're not sure about ferocity, you could go with a monster with multiple arms that get damaged and lose attacks as the combat goes on. Something like a hydra with 1 ferocity per head and it starts with 1d3+1 heads. Plus typical hydra shenanigans. That's in the Bestiary.
I tend to stick with one-time magic items. D&D-like gear with straight bonuses strikes me as boring. I wouldn't want to use anything like a bag of holding as it renders the hard-scrabble aspects of the game moot.
I don't necessarily know about the original DoD, but the upcoming Book of Magic supplement will include and discuss magic items.
In the earliest days, magic items were pretty much ad-hoc. I think there were some examples in the core book but not many. With the release of the Expert rules, magic item creation became codified and highly connected to actual spells. Basically, creating items was based on three spells/rituals: Sigil (hold a spell for a one-use item), Permanence (make a Sigil permanent so it can be used indefinitely, costing power points each time used, and Permanence itself costs one permanent Power), and Nexus (make a Sigil self-powered, costing the caster 2 points of permanent Power for each spell). These spells were quite high level, so item creation was mostly kept out of PC hands. The Magic book in the Expert rules also had some examples of the rules in action – maybe a dozen or so items, many based on items of legend. Later books also had some items with non-spell effects but nothing codified.
In SotDE, a lot of the dungeon bosses are assigned Ferocity more as a formula than a standard number. The formula was either Ferocity=# of Players or # of players -1. I often ran games of five or six and the math worked reliably.
The new DB has a very similar set up.
I added 1 ferocity to the goblin / worg in the first encounter and it worked well for six characters. dangerous and scary.
