The Gnoll entries include a good variation in CR, and the
Flesh Gnawer comes in at a solid CR 1. This makes them pretty good for combat fodder for many levels - their HP and damage output keeping them at least relevant up until level 9 or so - and so you can probably expect to make heavy use of them after a while.
The Flesh Gnawer picture in Volo’s has a lot of character. Though it is very static - in essentially the same pose as the Flind and Witherling - the Gnawer has a very well done face, which is busily emoting a deranged world view to the observer. I’m also quite taken with the human hand which is jauntily stuck into the waistband, a nice snack for later.
The Flesh Gnawers get a flavour text so short that it barely counts as present. They are more feral than other Gnolls, they don’t bother with ranged weapons, and they can run fast to finish off enemies. The Gnoll section in chapter one says essentially the same thing - they lurk around at the start of battle, and then rush from wounded warrior to wounded warrior as though ‘shot from a bow’. In other words, you should use these guys as generic dudes for the players to kill in the game, they do not have hidden reserves of roleplaying potential for you to tap.
As I mentioned above, the Gnawer comes in at a useful CR 1. You can pretty much use these guys for the whole of tiers 1 & 2, to varying degrees of merit, and they should at least do
something. Be aware, however, that your Cleric player will really start emphasising
Spirit Guardians after a while if you lean on them in every combat. That isn’t bad - the spell is effectively a class feature, and letting a player get use out of it is no bad thing - but be warned that you’ll need to mix in ranged dudes as well. Not to worry though - the next statblock is the Hunter, who has the ranged options covered.
This statblock is pretty standard for CR 1. You get 22 hp, medium AC, and stats hovering around the 10 on average. They get the
Rampage trait of all Gnolls, and they get three melee attacks for normal damage. The only really unique thing here is the
Sudden Rush ability, whereby the Gnawer can move up to 120ft [
Correction: 90ft.] a round and not provoke opportunity attacks. That sounds like a great way to have the Gnawers materialise in melee with the party backline, even if the Gnawers cannot attack afterwards, and in general means that you can put real pressure on the party to kill the Gnawers before they bring down the party squishies. It also makes them very effective at running away from fights that they are losing, so you could contemplate some kind of an ambush, with these guys drawing the players into a killzone with some Hunters or whatnot. Either way, this incredible movement is clearly the central mechanic of the Gnawer, and I imagine that most parties will really grow to hate these guys for that exact reason.