This happened in adventure league. The party of 6 came upon 3 manticores. Two paladins, a barbarian, a bard, a wizard, and my rogue.
Paladin 1, my rogue, and bard take on a manticore. Paladin 2 and wizard take on another. Barbarian solos the third.
I see after round one the barbarian is going to get screwed so bad with all the tail hits. I need to do something. I had just reached the arcane trickster at level 3, which means that I can now cast an invisible mage hand.
I ask the DM if there are thorny shrubs nearby. She says yes. I ask if I can drop a fistful with my magehand, she says yes. Immediately I tell her I move the mage hand as fast as can be possible, and jam a fistful of thorns up the manticores butt. She wanted me to do sleight of hand, because as an arcane trickster i can apply that to certain dextrous movements.
Nat 20. Fist right up in there. Now, I wanted to pitch this in the most reasonable way possible. So I explained to her the following: every time one of the tails move, wouldn’t the rump muscles tighten? She agreed. I postulated that sharp stabbing pain would erupt whenever the manticore moved to attack. I didn’t want to cause it damage. Just disadvantage on the tail attacks.
The DM thought that was reasonable. The manticore didn’t land a single hit after that. The barbarian wrecked it so hard.
So yeah, I can say I fisted a manticore with a handful of thorns.