What is it ?

A mod adding mobs which could have been, but were never truly allowed into the game as others took their place instead;
It features a close interpretation of each mob vote contestants who previously lost , alongside structures and extra items.

What does it offer ?

Mobs taken straight up from the various mob votes, with one or two extra features to go with some of them.

I will talk below about my thoughts on all the creatures added by this mod (from most recent mob vote to oldest) :

The Crab :
An ambient mob, which can leave a large claw after his death, which can be used to make a reaching potion to get extra range for both combat and mining/building

The Tuff Golem :
Acts as a way to display items through a mob. It does what you expect it to
The Rascal :
A creature that you have to find three times inside a mineshaft in order to get a bundled reward.
Specific issues with rascal -> when used in combination with mods adding their own custom mobs to mineshafts, the rascals are often the only ones actually witnessed there (I have noticed that when using Alex's mobs, which has its lot of issues, it seems I'm forced to make the ghostly creatures appear in general caves if I want to see them alongside rascals within the same pack)

The Glare :
A way to know a place is too dark to prevent night monsters from appearing, it's about it in terms of use for this mob
The Copper Golem :
This one is a bit of a special case as Minecraft brought them back in very recent versions with a different chest-sorting behavior;
Here they act as redstone randomizers, randomly pressing copper buttons around them while oxidizing slowly over time (they can be found within custom village structures as fully oxidized statues)

The Moobloom :
A flower-planting cow. On the side, this mob is linked to the addition of a new decorative flower (the buttercup) and a beekeeper villager profession, which buys some flowers and sell honey in various forms
The Iceologer :
I used to think they made him too resilient, but I've just tested the last 1.21 version of the mod and it seems they decided to reduce its health, I think it's better this way especially considering that it made previous fights with him feel slugish.
That said I still personally don't really like that they decided on keeping the Minecraft Dungeons artstyle instead of readapting it for Minecraft's, it feels a bit too smooth/bland compared to the other mobs, but maybe that's just me, and I really don't like that it has an instant-freeze attack which can't be avoided at all. On death they give a totem of freezing, which is just a totem of undying variant with slight differences

The Mauler :
A neutral creature only hostile towards small animals, they can be given magical items to eat which can be turned into experience on their death or if you use glass bottles on them
The Wildfire :
A Nether mini boss concept which never got to exist (in the main game that is), added in his own structure instead of the nether fortress it was supposedly going to be added to originally, this creature has a close quarters area attack (a groundpound which can push you into the lava collumns in its arena), can shoot fireballs and summon blazes to call for help (but not too often as some other mods do); Killing him grants you fragments of his crown, that you can be crafted back into its original form to get it for yourself (grants fire resistance, which goes down rapidly after taking a bath in lava similarly to the turtle shell underwater; Works a bit less though, since being on fire is a state which tends to linger a bit even after getting out of fire-damaging areas).
Making it so the Wildfire's shields get slowly removed as you naturally fight it instead of granting him Minecraft Dungeons-like shield which need to be broken first before you can deal any damage makes the fight more smooth (serving more as an indicator of how far you're into the battle instead), which I honestly prefer and makes this wildfire one of my favorite "nether knight" concept

The Illusioner :
Another special case, as it was never even proposed as a mob vote candidate but was discarded due to technical constraints, the one added by this mob is heavily inspired by its Minecraft Dungeons incarnation in its looks and the way it creates actual clones instead of fake mob renders, I feel like Minecraft could actually add the illusioner this way in the base game if they ever made an update for him; He has his own totem variant called the Totem of Illusion, which is a modified totem of undying, meant to trigger in battle to trick your enemy when you get cornered

In conclusion

I think this mod is honestly decent even if it certainly feels a bit generic in terms of the additions added to some of the mobs; outside of that, it does what you would expect from it, and kept improving over time.
Edit : The configs are quite nice lol, don't remember why I forgot to even mention them, I again wish you could configure illusioner and iceologer waves with more precision than just a yes/no answer to their presence within raids.
I personally don't think adding a custom structure for the Iceologer nor Wildfire was necessary as they would work better as naturally-spawning mobs within vanilla environments I feel, but that could just be the way I see it.

please ignore that I forgot about the Zombie Horse