I compiled all the evidence/my thoughts so you can double check me but I THINK IT'S BERYL YOU GUYS!! Here are my thoughts:
They seem very involved in a lot of this, and is straight up a bird. ALSO... WE HAVE NOT LEARNED THEIR PRONOUNS. SO THEY MAY BE MALE/MASON'S BROTHER. They have been noted to be very knowledgeable about the forest, having forraged for crafting supplies and having an overhead view of the forest, AND would also have access to paint to mess with the trail signs.
Motive for kidnapping Cirrus may be frustration with Glampers driving cryptids into the main camp--after all, arts and crafts pavilion was the first thing to get ransacked! We've been collecting Beryl's beads all week!
How does this relate to Seraphine's disappearance? Well, if Beryl was the one altering the signs, they probably didn't want Seraphine in the watch tower to be able to see them leading Cirrus away. So it would have been in their best interest for Seraphine to be preoccupied that night.
However i don't think the deal is sealed. I tried to un-biasedly collect the rest of the clues, and included my thoughts on potential other suspects:
MAJOR PLOTLINES:
-Cryptids have been encroaching on the main camp to a higher degree than normal, and i like the theory someone else posted about them being spooked out of the woods and into the main camp by the glampers.
-Mason's cryptid obsession, and brother's past of faking cryptid appearances. Mason says his brother hasn't done it in a while--but wait do we know if his brother works in the camp?
-Campers being inconsiderate/littering.
-Cirrus and Andrea having some kind of falling out around the time of the disappearance?
-PLAYER FOUND CLUES-
TEAM APPLE:
found orange fur under painted tree sign, and are pretty sure it belongs to Seraphine. it should be noted that the fur found at the cave was described as brown.
found that the trail signs were altered, and would have caused them to go the wrong direction.
BERRY:
Found an old sign calling the lake "Loch Tess".
Something big grabbed one of their members' ankles and tried to pull them under.
Saw the glampers heading out on canoes with their gear.
CHICKEN:
Learned mason's brother faked a BIG BIRD WITH RED EYES - which is identical to what we have been seeing from a lot of the pets!
Seraphine didn't believe in cryptids and that annoyed Mason.
Mason was very fed up with glampers and their improper camping.
CHOCOLATE:
Firewatch tower didn't seem disturbed but there was some old rope & an old spoon.
Found cirrus's bracelet by the lake, found permanent marker used to write on Cirrus's food bag, found that fairy lights are considered "dangerous"
CREAMSICLE
Bear bag interference - bags were too high for a bear to have messed with.
Some glampers have been irresponsible about not putting their food up in bear bags because it's not meat.
Clue about two figures in the woods--feels like this was explained by Cirrus walking strangely because she was stumbling though?
GREEN
Saw trail marker paint and trail maps in Seraphine's watchtower.
Saw 2 figures on the Glamping "Fintastic" boat in the lake.
Found rhinestones that were confirmed by Beryl to be from Cirrus's necklace, gifted to her by Andrea.
VANILLA
Learned Andrea is very upset--but wouldn't say why.
Learned Seraphine is newer to camp.
Learned Conall is surprised that Cirrus wanted to learn how to make a campfire because she is not the outdoorsy type.
Beryl is making a painting with stars that looks like eyes.
-NPC CLUES:-
CIRRUS'S KIDNAPPING:
Someone DID kidnap Cirrus--it was not an accident! She was snatched, blindfolded, and led away.
They did not speak to Cirrus or state their intention.
Once Cirrus was awake they saw loads of tracks near the cave, and saw a tuft of brown fur.
Felt like they were being watched and heard wings.
Glampers saw two figures--one walking strangely.
Conall said fur from the campsite smelled weak, as if whatever left that hadn't been around in a while. so whatever left the fur is probably not responsible.
SERAPHINE GETTING LOST:
Seraphine says they simply got turned around, and no one messed with them.
They were looking for a raspberry grove Mason told them about.
Compass unexpectedly broken, trail signs had been altered so they got lost.
CONALL SNIFFING AROUND:
Smelled a similar scent by the caves to the animals that have been coming into the main camp, but didn't get much from the fur. Thought it was similar to owls, but was a bit off.
SUSPECTS:
-a LOT seems to be pointing towards Mason and/or Mason's sibling, or the cryptid they were imitating; the red eyed bird pops up a lot in the pets we have been given. Also, Cirrus mentioned hearing wings while kidnapped and the bear bags were messed with by something that can get higher than a bear. Other cryptid tracks/fur around the cave were older and Conall only caught a scent of the "owls, but slightly off" which makes me think it MUST be somewhat bird related. However i am increasingly less suspicious of Mason because he doesn't seem like he would fake a cryptid sighting because he is so convinced they are real, and the cryptids themselves seem pretty peaceful from what we've seen of them in camp now. I suspect his bro/someone else from their hometown with the same idea may be behind it. I suspect Beryl for this!
-As pointed out earlier, Seraphine seems to be very experienced and it's strange that they would get lost so easily. While it does seem feasible that they were indeed sabotaged by someone with even MORE knowledge of the forest, we should probably take what they say with a grain of salt.
-Moose has been VERY adamant about trash and respecting wildlife, moreso than the other counselors. He's also specifically been very defensive of Tessie despite "not believing" in cryptids. Lunu as well. I feel out of the counselors they may have the strongest motive to try and teach campers a lesson. With the spoon and old rope being found by the firewatch tower I wonder if Moose may not be Mason's brother? The old rope being how he hoisted himself to fake flight, and the spoon just a hint it was someone involved with food?
-Also, incredibly suspicious of the Glampers. team Chocolate found Cirrus bracelet on the far side of the lake, and we know Glampers have canoes. Also, the mention of the 2 figures on the boat in the middle of the lake! And how they packed up and cleared out like ASAP. I'm not sure what their motive would be though. Maybe we need to ask Cirrus whose boat is the "Fintastic" so we can get more specifics on what's going on with that.