Toady One writes on the Dwarf Fortress Development Log:

As many of you know, forgotten beasts come in all colors. In our initial graphical release, we made some evocative silhouettes but didn't have time to do them justice. Jacob has been doing a great deal of justice lately.

I was attacked by my first forgotten beast. We had two casualties, which was not bad considering the nasty critter it was. It flung one of my archers into the lake near where the fight went down.

I also finally started messing around with the justice tab and oh man that’s fun. I’ve been having artifacts go missing randomly and it turns out there’s a plot behind the thefts and one of my military squad captains was behind some of it! So I’ve been investigating the espionage, which has been super fun to see unfold.

Thol was a forgotten Beast. A gigantic skinless bison twisted into humanoid form. It undulates rhythmically. Beware its poison gas!

Our first forgotten beast, Bomrek, was a giant salamander.

It had poison gas, but I don't think I saw any effects from it.

It was scary, and skulked around our cavern lakes for a long time, but ultimately not too bad.

Uzol FIghtsteel got to finish him off. I gave here the nickname "beast basher" (that's who has a bunch of family heirlooms, I'm still not sure why exactly)

Some other stuff happened, made deals with Elves, Humans and Dwarfs.

Finally starting to get down to dry stone. I'm still struggling to get things built and equipment crafted.

I think here is when we got our first hostile goblins

I don't remember, I think we had one or two waves of sad little thieves, and at least one got got by the swarm of dogs I have out front.

Next forgotten beast was a terrible shrew.

This one gave us some trouble.

We bruised the hell out of it, but just weren't getting enough damage.

Two things that didn't work out,

1 is, I had an idea to have my two were-ape citizens tucked away in a little hideaway personal tavern, and then send 'em out

Timing didn't work out at all, we engaged way sooner than I expected.

Azstrog ate a recruit I'd lost track of, pretty much everyone rushed in haphazardly. Cranky with no equipment, just biting and clawing. Valiant effort, did not survive.

2, then This guy

intelligent undead, monster hunter, talented mace dwarf, visiting my fort,

start heading down towards the fight, gets my hopes up

but no,

he's just he's just leaving. Walks right past the commotion, exiting through the caverns.

Multiple casualties, I sorta lost track of some things.

Numbers' memorial slab says he bled to death, but I'm pretty sure what actually happened was he got beast sickness, and then later fell out of a tree and drowned. I forgot to take screenshots.

We also lost Carpenter, and I don't remember which forgotten beast took off a chunk of FishEater's leg.

Then,

Rodent Mans

These dweebs had Steel Weapons

They charged in from caverns, and decapitated some chickens

then some stuff didn't happen*

I don't think we lost anyone there, but we took some hits. Rith, our baroness, in particular had it pretty rough.

She hasn't let it slow her down. She was pretty quickly up, drinking wine, instead of getting the bronze spear** lodged in her chest diagnosed in the hospital.

Then, up on the surface,

A goblin siege.

It was only a small number of goblins, but they had cross bows, which they could actually use as ranged weapons, and it's not fair.

The got Rith's poor husband, Aban

Also two humans that I felt bad for sending to their deaths, but they were cranky and kind of bringing down the mood of the fort.

*the rodent mans didn't cut both hands off my expedition leader, and then they didn't interrupt a strange mood making me have to send a squad to murder a citizen.