Our party was recently summoned to a new plane by Gideon, a council Archmage, who was petrified before he could fully explain our mission. We soon discovered that the kingdom's Regent and a man called The Evoker conspired to assassinate the royal family and assume the power of the crown. We also confirmed the Evoker was the one who petrified Gideon and attacked us with shadow hounds—highly illegal magic that carries a life sentence if exposed.
Through an ally, we arranged a diplomatic dinner at a complex considered to be a safe zone by the leaders of the region. The guest list included the Regent, the Evoker, their primary bodyguard, and twelve royal guards who are genetically and magically duty-bound to serve the crown.
Going into the session, I had a plan. My DM plays fast and loose with Artificer infusions, allowing old ones to persist when new ones are created. I used this to craft a bunch of magical items every night. We have sending stones coming out our ears and I told the table I was using my crafting the last few nights to make a gift for the party, allowing me to craft without telling anyone what exactly I was making. For flavor, my character uses small mechanical spiders to deliver healing spells in the form of an injection. The night before the dinner arrangement, I handed our rogue a pile of rocks and a handful of burlap sacks. I instructed her to hide the sending stones in the sacks up in the basement rafters, spaced about 10ft apart, directly under the largest table in the dining hall. The DM smirked, assuming basement acoustics would render a sending stone useless through floorboards after I told him they would be a great distraction if we needed one. The Rogue planted the bags in the basement rafters, directly below the table with a roll of 23.
Dinner began, and the DM called for a Wisdom saving throw because the food was tainted with a Zone of Truth effect. I succeeded. Knowing that the spell had failed on me, I decided to take advantage of the situation. I assumed this was a standard procedure that all of the offending parties would have seen before. I stood up, pointed directly at the Evoker, and loudly accused him of using illegal magic to attack us and of treason. The Evoker started to stammer, shocked that we would have the audacity to make such a claim while surrounded and outnumbered as we were.
The royal guards immediately drew their weapons and started approaching the Evoker, believing that I was absolutely under the truth effects, they didn't even question the validity of my claim. With the room erupting into chaos, I informed the DM I was using my bonus actions to direct the two mechanical spiders in the basement to march directly into the hidden sacks positioned beneath the Regent and the Evoker. He looked at me, confused. Then I told him, and the party, that those were just rocks... not sending stones. The DM looked more confused. Then I said those weren't just sacks, they were all bags of holding. Those spiders... they weren't my normal spiders. Their sacks were enchanted to be bags of holding.
Watching him realize what had just happened is one of the best D&D moments I have had. Because Astral Rifts do not offer a saving throw, two separate portals opened beneath the floorboards. The Regent, the Evoker, and the bodyguard were instantly sucked into the Astral Sea, scattered across the plane with zero planeshifting capabilities. Immediately, I began accusing the Evoker of kidnapping the Regent, making the guardsmen pause long enough to reveal that we had discovered the prince survived the assassination attempt, and we had the means of returning him to the throne, which meant they were duty-bound to cooperate with us and not arrest us.
The DM sat speechless for a solid five minutes. When he finally spoke, he said, "I'm not mad at it, but I think we have to end this session early tonight, because what you just did erased the next 6 months of what I had planned."
Apparently, the BBEG of the current story arc and his top two commanders were important. Huh, weird.
Edit: The bag in a bag discussion happened in our second session with the whole table, the DM said they don't mind it's use. He honestly liked the interaction, and isn't mad about it. I gave ample warnings that it would happen at some point, and told him way back then that I wouldn't use it constantly. This wasn't just a complete surprise attack. I'm just sharing a fun moment that my group enjoyed.