I saw a thread in the discussions where people were discussing the mythical creatures and a lot of folks seemed to have only seen a few, so I thought I'd make a list of all the creatures and events I'd found. Don't read if you don't like spoilers.

This list is very incomplete, and for anything without a screenshot I'm working from memory. If you have more info please comment and I'll add it to the guide!

All buffs last only for the day they're found on. You can see any buffs by looking at the wall inside your shop where the counter joins it. There will be a small orb there for each buff, hover over for details.

How to tell if it's active: N/A, always available
Directions: Turn right out of the shop, follow the river to its source then turn right
Buff/effect: +10% Profits
In-game name: Ulmbrow's Light

---

How to tell if it's active: Pops out of the lake when you get close. Appears when the weather is rain (I think, I've seen this combo twice so far)
Directions: Turn right out of the shop, follow the river to its source
Buff/effect: +15% Profits
In-game name: Water's Blorb
Note: Unlike other creatures you don't need to click on it, just go near it and you'll get the bonus

---

How to tell if it's active: Immediately visible when you leave your house
Directions: Turn right out of the shop
Buff/effect: +15% Profits, +3 fruit harvest amount
In-game name: Verdhorn's Path

---

How to tell if it's active: Visible from home (from shop entrance, look slightly left and up above the cliff)
Directions: Go down the hill into the water and follow the cliff around to the left
Buff/effect: +25% profit, x2 crafting output
In-game name: PATCH's Insight

---

How to tell if it's active: Visible from home
Directions: From shop, look straight forward and down, it will be visible on the left side of the island
Buff/effect:
In-game name:
(screenshot pending)

---

How to tell if it's active: Visible from home
Directions: From shop, look straight forward and down, it will be visible on the far side of the island, you have to walk into the sea to reach it
Buff/effect: +25% profits
In-game name: Azurthaal's Tide

---

How to tell if it's active: It will fly over your house as you leave in the morning. The magic floating stone (left when leaving your shop) has a big beam shining from the top, and a big triangular floating island will slowly fly over the map.
Directions: From shop, turn right 90º and cross the low bridge, it will be on the plains on the other side of the river
Buff/effect: (TBC, I think +3 mining?)
In-game name:

---

How to tell if it's active: The magic floating stone (left when leaving your shop) has a big beam shining from the top, and a big triangular floating island will slowly fly over the map.
Directions: Go through the apple orchard and up the slope on the right, follow the path around through a valley to get to the top of the cliff
Buff/effect: +15% profits, +3 tending amount
In-game name: Ruby's Torch
Note: There is a second reddish dragon that flies over your house in the morning sometimes, but it's not the same as this one and I don't think it lands anywhere for you to visit.

---

How to tell if it's active: Visible from home
Directions: From shop, turn left and go around the corner, it will be between the two cliffs
Buff/effect: +15% profits, +3 mining amount
In-game name: Obryl's Shine
Note: I think I've seen more than one type of these, but they both were in the same place and gave the same buff

---

How to tell if it's active: Visible from hill next to shop
Directions: From shop, turn right 90º and cross the low bridge, it will be on the plains on the other side of the river
Buff/effect:
In-game name:
Note:
(screenshot pending)

---

How to tell if it's active: Visible from shop, is walking slowly in the background
Directions: I didn't think you could reach this one, but I saw someone say you could if you set up ziplines beforehand. I haven't yet managed it, but I was able to walk to a place where it seems likely you could reach it (from the big island, look across the water and there's a mountain with a shallow left hand side. Note that if you put a single zipline on the mountain it's too far to click on, you need to chain them over the water)
Buff/effect: Not sure it even gives one
In-game name:
Note: There are at least two, walking in opposite directions.

---

How to tell if it's active: Visible from shop, in sky next to big crystal
Directions: (not the quickest way, but the easiest directions to write and follow) From the shop, go downhill and into the water, and around the cliff to the left. Keep following the cliff until you find a big ramp, and go up it. From the top of the ramp there are no obstacles, you can just run there directly
Buff/effect: +50% profits
In-game name:
Note: Things get kinda strange and glitchy when you go this far from the official map, don't worry you're still going the right way. You can teleport home from the Esc menu to save time.
Credit: Thanks Fox in a human disguise for commenting that this was a valid creature

---

Unlike creatures, events usually happen at some point through the day instead of being available all day. For at least some, you can see a sign they're going to happen in advance though (maybe for all, but if so the signs are subtle enough for me to miss).


How to tell if it's active: Look at the sky, you'll see lots of shooting stars
Details: Later in the day, a large meteor will fall from the sky and land downhill from your shop (From the shop door, straight ahead and slightly left, on a patch of ground which is bare earth every day)
Buff/effect: You can mine the meteorite pieces for 30 starshard crystal (before skill bonus)
In-game name: N/A
Note: You have to mine it the same day it falls, or it disappears. No waiting for a mining buff! This is the only way to get starshard
(screenshot pending)

---

How to tell if it's active: Not sure
Details: Later in the day, a glowing white unicorn will appear next to your house. If you approach it, it will explode into shards
Buff/effect: You can mine the shards for 20 lunacite crystal (before skill bonus)
In-game name: N/A
Note: You have to mine it the same day, or it disappears. No waiting for a mining buff! This is the only way to get lunacite
(screenshot pending)

---

How to tell if it's active: Not sure (when I saw it last it was the same day as a rainbow)
Details: Later in the day, a glowing pink unicorn will appear next to the customer portal. If you approach it, it will explode into shards
Buff/effect: You can mine the shards for 20 dark lunacite crystal (before skill bonus)
In-game name: N/A
Note: You have to mine it the same day, or it disappears. No waiting for a mining buff! This is the only way to get dark lunacite
(screenshot pending)

---

How to tell if it's active: Not sure if you can tell in advance, but you don't need to do anything
Details: Early in the day, a mage will walk into your shop and cast a buffing spell
Buff/effect: +25% profits
In-game name: N/A
Note:

---

How to tell if it's active: Visible in sky
Details: According to the outofboundium guide by SinfulWun you can go to the rainbow ends for outofboundium crystals to mine. Will confirm when I unlock ziplines in my current game.
Buff/effect: Mineable outofboundium
In-game name: N/A
Note: There are much easier ways to get outofboundium

---