Mirna

Monsters you meet here

Monster	Role	Tier	Health	Speed	Experience	Loot chance	When it arrives
Slug	Common monster	Common	10	0.8	10	0.5%	All the time on its own: 90 a minute at the start of a run. Sometimes on the clock: Every 75 s; Every 30 s (only part of the time, or only later in a run).
Worm	Interloper	Common	50	1.2	10	0%	On the clock: Every 104 s.
Sprinter	Sprinter	Common	10	2.4	25	5%	Sometimes on the clock: Every 75 s; Every 60 s; Every 49 s; Every 30 s (only part of the time, or only later in a run).
Big Slug	Elite	Elite	150	0.8	150	100%	Sometimes on the clock: Every 150 s; Every 75 s; Every 60 s (only part of the time, or only later in a run).
Bomb-omb	Bomb	Bomb	10	1.75	25	0.5%	Sometimes on the clock: Every 120 s; Every 75 s; Every 49 s (only part of the time, or only later in a run).
Bomb-omb Big	Elite bomb	BombElite	50	1.5	75	0.5%	Sometimes on the clock: Every 120 s; Every 75 s; Every 60 s; Every 49 s (only part of the time, or only later in a run).
Big Zap	Miniboss	MinibossElite	500	0.75	500	100%	On the clock: Every 300 s.

This is the roster a run starts with, stage 1 of the region's spawn setting. Each miniboss you kill moves it on a stage, so others take these roles later in the same run (see how the roster changes, below).

Boss

Boss	Snake Boss
Health	2500
Speed	3
Experience	3000
Seconds between attacks	5
Region reward	Mana Crystal Slab
Corrupted-region reward	Crystal Fang

It fights faster once it drops under half its health, and beating it is what opens the next region. Its own page has the full pattern.

Who appears when

The common monster of the current stage arrives on its own all the time: 90 a minute at the start of a run (180 in the final battle and on hard mode), spread over one spawn tick every 0.25 seconds, each tick up to 33% above or below the average.

At the start of a run that is Slug.

While a boss fight is on, it is 180 a minute instead.

A run opens with 5 of them at once.

No more than 300 monsters are on the field at once: a spawn that comes while the field is full is skipped.

The wave number starts at 0 and goes up by one every 60 seconds; many counts below grow with it. A change to common monsters a minute is worked out from the normal starting rate, so a stage that scales the rate scales those changes too.

When	What arrives	What else changes
Every 1000 s	Death: one arrives, 1.5 screens out	nothing
At 2:00, then 600 s later for every boss you have killed while no boss is on the field	nothing new	your magus says "Something's coming…" the screen shakes
At 7:30, then 600 s later for every boss you have killed while no boss is on the field	nothing new	your magus says "It's getting closer…" a boss distance readout counts down from 10000000 metres to 0 over 150 seconds
Every 600 s	Snake Boss: arrives, and the boss fight starts	52.2 fewer common monsters a minute (-58% of the starting rate) the music turns tense
Every 300 s	Big Zap (miniboss): one arrives, 1.5 screens out Thrower: a surge, one per 3 minutes survived (with Shifting Tide)	54 more common monsters a minute (+60% of the starting rate) a cage is drawn around you: it pens you in, and brings no monster with it monster strength +0.5
Every 150 s only when the 300 s step does not fire on the same second	Big Slug (elite): one arrives, 1.4 screens out Thrower: a surge, one per 3 minutes survived, at least 1 (with Shifting Tide)	monster strength +0.25 18 more common monsters a minute (+20% of the starting rate)
Every 120 s only when none of the 300 s, 150 s steps fires on the same second	Bomb-omb (bomb): a surge, one per minute survived Bomb-omb Big (elite bomb): a surge, one per 3 minutes survived (from 6 minutes in) Bomb Thrower: one arrives, 1.4 screens out (from 11 minutes in, with Shifting Tide)	29.7 fewer common monsters a minute (-33% of the starting rate) monster strength +0.1
Every 120 s	nothing new	the nearest unopened chest is marked on your map
Every 104 s	Worm (interloper): 2 per minute survived drop in as one clump, each with +1 on top of the strength multiplier	nothing
Every 75 s while no boss is on the field, with Hazard Pay	nothing new	3 to 8 Hazard Pay traps drop around you, 20 to 40 units out, scaling up over 20 minutes
Every 75 s while no boss is on the field	a full ring closes in around you, each with +3 on top of the strength multiplier at the start of a run, rising to +20 by 60 minutes: Bomb-omb (bomb, 50%), Sprinter (sprinter, 50%) (the 4th firing, then one firing in 3) a full ring closes in around you, each with +3 on top of the strength multiplier at the start of a run, rising to +20 by 60 minutes: Bomb-omb Big (elite bomb, 80%), Big Slug (elite, 20%) (otherwise, the 6th firing, then one firing in 5) Slug (common monster): a full ring closes in around you, each with +3 on top of the strength multiplier at the start of a run, rising to +20 by 60 minutes (otherwise, not the first firing)	nothing
Every 60 s only when none of the 300 s, 150 s, 120 s steps fires on the same second	Big Slug (elite): one arrives, 1.4 screens out Sprinter (sprinter): a surge, one per minute survived Bomb-omb Big (elite bomb): a surge, one per 3 minutes survived (from 5 minutes in)	90 more common monsters a minute (+100% of the starting rate) monster strength +0.1
Every 49 s while no boss is on the field	10 drop in as one clump, each with +1 on top of the strength multiplier at the start of a run, rising to +1.5 by 10 minutes; how many clumps: a random number from 1 to 0.4 per minute of run time, rounded down: Sprinter (sprinter, 65%), Bomb-omb (bomb, 30%), Bomb-omb Big (elite bomb, 5%, until 5 minutes in, Sprinter instead)	nothing
Every 30 s only when none of the 300 s, 150 s, 120 s, 60 s steps fires on the same second	Slug (common monster): a surge, 1.5 per minute survived, rounded down Sprinter (sprinter): a surge, one per 2 minutes survived (from 2 minutes in) Thrower: a surge, one per 5 minutes survived, at least 1 (from 20 minutes in, with Shifting Tide)	nothing

Monsters in this table are the ones of stage 1, the roster a run starts with; each role is filled by the current stage's monster, see how the roster changes below.

While you extract

While you extract (never in the final battle), every spawn tick also rolls this table once for every 30% of the common monsters it brought. Each roll is out of 100 and picks one line.

Monster	Chance	How many	Where
Big Slug (elite)	30%	1	2 screens out
Sprinter (sprinter)	20%	3	1.6 screens out
Bomb-omb Big (elite bomb)	25%	1	2 screens out
Bomb-omb (bomb)	20%	3	1.6 screens out
Big Zap (miniboss)	2%	1	3 screens out

The other 3% of rolls bring nothing extra.

How the roster changes

The roster moves on one stage every time you kill a miniboss.

Nothing on the clock moves it, so a run that leaves the miniboss alive keeps its starting monsters for as long as it lasts.

After stage 5 the next move goes back to stage 2, and the loop carries on from there.

Every move past the last stage also makes every monster except bosses faster: +0.25 to their speed multiplier each time, up to 2 times their speed.

Stage 1 is where every run starts; its entry changes never apply to that first stage.

Role	Roster stage 1	Roster stage 2	Roster stage 3	Roster stage 4	Roster stage 5
Common monster	Slug	Snailshroom	Worm	The Thing	Slug
Interloper	Worm	The Thing	Slug	Snailshroom	Worm
Sprinter	Sprinter	Sprinter	The Thing	The Thing	Sprinter
Elite	Big Slug	Jellyshroom	Jellyshroom	Jellyshroom	Big Slug
Bomb	Bomb-omb	Bomb-omb	Bomb-omb	Bomb-omb	Bomb-omb
Elite bomb	Bomb-omb Big	Bomb-omb Big	Bomb-omb Big	Bomb-omb Big	Bomb-omb Big
Miniboss	Big Zap	Big Zap	Big Zap	Big Zap	Big Zap
Common monsters a minute, on entering	-	x0.33	x0.93	x0.93	x0.93
Monster strength, on entering	-	-	+0.1	+0.25	x5
Surge on entering	-	Snailshroom: 5	-	-	Slug: one per minute survived

The first 10 minutes

The same rules run second by second and grouped by the minute they land in, with no miniboss killed, no run modifier active and every step that waits for no boss on the field treated as clear. The common monster's own steady arrival is left out.

Minute	What arrives, and when
0-1 min	0:49 Sprinter Bomb-omb
1-2 min	1:00 Big Slug 1:30 Slug 1:38 Sprinter Bomb-omb 1:44 Worm
2-3 min	2:00 Bomb-omb 2:27 Sprinter Bomb-omb 2:30 Big Slug Slug
3-4 min	3:00 Big Slug Sprinter 3:16 Sprinter Bomb-omb 3:28 Worm 3:30 Slug Sprinter 3:45 Slug
4-5 min	4:00 Bomb-omb 4:05 Sprinter Bomb-omb 4:30 Slug Sprinter 4:54 Sprinter Bomb-omb
5-6 min	5:00 Big Zap Bomb-omb Sprinter 5:12 Worm 5:30 Slug Sprinter 5:43 Sprinter Bomb-omb Bomb-omb Big
6-7 min	6:00 Bomb-omb 6:15 Slug 6:30 Slug Sprinter 6:32 Sprinter Bomb-omb Bomb-omb Big 6:56 Worm
7-8 min	7:00 Big Slug Sprinter Bomb-omb Big 7:21 Sprinter Bomb-omb Bomb-omb Big 7:30 Big Slug Bomb-omb Big
8-9 min	8:00 Bomb-omb Bomb-omb Big 8:10 Sprinter Bomb-omb Bomb-omb Big 8:30 Slug Sprinter 8:40 Worm 8:45 Bomb-omb Sprinter 8:59 Sprinter Bomb-omb Bomb-omb Big
9-10 min	9:00 Big Slug Sprinter Bomb-omb Big 9:30 Slug Sprinter 9:48 Sprinter Bomb-omb Bomb-omb Big
10-11 min	10:00 Big Zap Slug Snake Boss

Difficulty ramp

Monster strength multiplies every monster's health and the experience it gives, once it is above 1. Monsters a minute is how many of the common monster arrive on their own between the steps.

What that adds up to

The same steps worked out on the clock, with no miniboss killed and no boss fight. Every miniboss kill moves the roster on a stage and can change both numbers, so a real run usually climbs faster than this.