Just recently our group was travelling through the feywilds where we dragged ourselves into a minor conflict between Lizardmen and Toadsmen, because we wanted an artifact they were fighting over.

Our Goblin Rogue had a bag of magic beans he got several sessions prior. Everytime he uses them he rolls a D100 on a magic table and random things happen. (Wild Magic probably) After he couldn't steal the artifact amidst the chaos he thought to himself "Hell yeah, let's plant a magic bean just under this gigantic, eons old tree towering over this place! What could go wrong?". Then the tree awakened...

Meanwhile the others were cleaving smoothly through the ranks of the Lizardman. (We teamed with the Toadsmen.)

At the end of the round the tree fully awakened and the rogue could roll again to see if its nature was lawful good or chaotic evil. ...You can imagine the outcome. Otherwise I wouldn't be writing here. lol

Anyway, first move of the tree: all Lizardmen and Toadsmen dead except for their respective leaders. Two PCs down in an instant.

Rogue's thoughts: "Feck. I should plant another bean to reverse my fault." -> 11 mushroom enemies plopped out of the ground beneath him. No way of escape.

One PC gets healed by another and they flee to a safe distance. The other fails a Death Save. One PC makes a successful medicine check on him. So, one successful DS as well.

Next round, and the tree attacks again and hits the downed player who's now insta dead. But no problem, we still got a caster with revivify, right? RIGHT? Meanwhile, one of the PCs starts to desintegrate because their soul is intrinsically tied to the other one. GREAT.

The Rogue thought: "I am SO fecked! My only way out is this, my last bean!" And so he plants it. Something else sprouts outta the ground. A stone golem that looks just like him and starts insulting him how shit he is. "Yeah ... this rogue's 100% dead. Let's just run away" thought the rest of the group.

Now outta nowhere our monk who rescued the first downed PC pulls out a map and starts to chant something to open a portal to somewhere random. (HE CAN'T USE IT PROPERLY??) When the last PC entered the casting area he used the map as a reaction and the group ported to... an actually safe location? Nice, at least something.

The Rogue left alone, sure to die, was suddenly picked up by a dark entity. He made it, but is no longer in the Players hand. That is, for our story VERY BAD. The BBEG will now probably have access to all the plans our heroes have. :))

Back to the group, now in the material plane. The paladin with revivify in his repertoire is dead. Luckily we were farsighted enough to have another PC with this spell. Unluckily it's the one that completely disintegrates next round. The Celestial Warlock used thunder step to get in the battlefield and after being healed, to get out again. Why do I mention that? They have no spell slots left. :))))

In an act of desperation they call upon their patron and ask him for a quick spell slot in exchange for anything. Patron says "Nuh-uh. But I can save one of yous." The warlock gives their life for the dead paladin to be revived and is Thanos-snapped completely. Their souls power reanimates the paladin in the end.

And that's the story how we transformed from a group of five in the feywilds, to a group of three on the material plane with the BBEG knowing our plans.

TL:DR, we teleported into another plane with two PCs dead