In this scenario the party has just entered the lair of the "Beast of Burlenbog" based on a random encounter from a system less third party adventure. The GM has just finished describing the picture above. Initiative has been rolled.
Chuck (Abraham): Ok due to my terrible luck I somehow go first. I am going to try to continue staying hidden and sneak past it to the hallway behind it.
The GM thinks, what is the stealth modifier of this beast? He thinks back to the monster generator in the 2nd Edition Acidic book. Step 1 is the perception. It has a long snout and pig nose so probably descent, then he sees the eyes on the wings. Are they just decoration or real eyes? According to the module its a magical fire breathing beast that is near impossible to sneak up on. The GM decides those eyes work and the creature is Supernaturally perceptive. Are there any other benefits it would have? Its not an ambush predator or unseen stalker, so no. Being Supernaturally perceptive it thus has a +7 perception modifier which gives it a +7 stealth modifier.
GM: Its alert to trespassers, and its calm, so it has a 17 to spot you.
Chuck (Abraham): Sheesh, I roll and get a 15, so its a hit not critical
GM: Being supernaturally perceptive it rolls a d20 for suspicion and gets 13.
The GM thinks, should it have a skill or background? It never leaves this lair due to a curse so its had time to learn every nook and cranny in it. The GM gives it a background for living in its lair.
GM: It adds its background for living in this lair and gets a 14 total.
Chuck (Abraham): Is that modified by size? You said this thing is big, how big is big?
GM: its as big as an ox, so that would make it size 2. You suffer 7 suspicion.
Julia (Brother Cadmus): No way we are getting past this thing, You might want to just take the suspicion.
Chuck (Abraham): Ya, that makes sense.
Julia (Brother Cadmus): I go next, with a loud prayer to St. Leeroy of Jenkins I try to smash it with a club. If its not interrupting ... no?...17.
The GM now thinks of the creatures combat abilities. He already decided that having the animal limbs it does that its quick (13A) so that is +1. The creature is driven by rage to kill everything it sees so the Hyper-Aggressive tag would work, that is a +5 to combat. That is a total of 16.
GM: It tries to scurry out of the way with a ..natural 20. Hrm
The GM thinks again, does it have any specific combat tricks that would come into play? It has a lashing tail, so the "Tail Swipe" trick is appropriate.
GM: It counters you with a swing of its tail, a large blunt weapon. Oof, bad roll. 12 total.
Julia (Brother Cadmus): I roll a 13 on my defense, so I dodge its tail.
GM: It goes next, so.. it will, hrm..
The GM thinks, it has paws so it could swipe with them with claws (they would be small, slashing attacks). It could use its tail again. It could bite (sharp teeth and long snout would combined to give it a medium piercing attack).. but it can also breathe fire. The two default options are the classic firebreath or the more recent cinematic "explosive balls of fire".
This is a janky old illustration so classic firebreath it is. The creature is supernatural so an amount of manage equal to its health seems fitting. 10 mana since nothing about the creature seems unusually vital or sickly.
GM: Its going to breathe fire at power level 3, which is going to go after 3 people hiding among the stones, so no Julia, to flush out whomever caused that suspicion. So everyone but Julia roll a repeating luck die. Highest luck is the one not hit.
Tom (Jack): That would be me with 18.
GM: Ok, so its an innate spell it will automatically cast..
Tom (Jack): I want to interrupt to fire an arrow. I have swashbuckler so I shout "Looks like you got stuck between a Rock and a Bard place fiend!", getting 17 on my appeal.
Everyone groans.
Kim (Thaugo): Are you fucking serious?
Tom (Jack): Because you see I am a bard, and there are rocks on the other side of him. Its great. Its already gone so I spend an extra action to double down and turn that into a statement.
The GM tries to figure out its presence. Its an isolated beast mutated from a petulant man-child of a priest a century ago. Its probably terrible easy to anger and manipulate. So its very uncharismatic. 4 Charisma is a base -2 to Charisma. It doesn't have any other tags that would give it a bonus. So its got a -2.
GM: It rolls a 14, -2.. making that still a critical success. A critical success on a statement gives you three successes.
Tom (Jack): I do an intelligence die, take the max result, and double it. With swashbuckler I am choosing to make that take away luck if it has any.
The GM thinks, its a named creature, how famous is it? If released it could terrorize the whole bog and the surrounding peat mining villages. Its a regional threat. That means it has 3d6 luck and 3 fate. Its luck die is a d6 so it has up to 18 luck... which..
GM: Wait, how much luck do you drain then?
Tom (Jack): 24
The GM doesn't bother rolling, so its got three fate left. Its out of luck
GM: Ok so now it breathes fire..
Tom (Jack): I still get to fire my arrow right? The swashbuckler gave me a free appeal
GM: Right, so your attack.
Tom (Jack): Natural 20
GM: (Sighing) not a natural 20, this fight is going to be real short isn't it.
Tom (Jack): I roll a d6 for damage, spending my other success to double it, and get a 2. I spend a fate to re-roll it and get a 6! Its repeating so I roll again and get a 5. I have +1 for perception so the total is 24 damage!
The GM thinks, its hide isn't particularly tough, nor does it have a carapace or thick scales. So it has no natural armour. Its size 2 so that is 12 damage. Its strong looking so that would be 13 Strength would still drop it and have it be dying. Time to roll those fates for more luck.
GM: So it starts expending fates for luck. I roll a 1 on the first d6. Not great. 2, still not great. And 2 again. It avoids 5 damage, dealing 7, and still dropping it to the ground incapacitated and bleeding out.
Kim (Thaugo): Aww... I didn't get to go.
The GM thinks to themselves, "I am so glad this isn't one of those games where setting up a monster stat block takes 45 minutes of work".