A Legacy of Intimidation

"Don't stay up too late, Papa!"
"I will stay up exactly long enough!" The man chuckled as he turned away from the door to return to his workbench. Behind his teasing lay the certainty that he would not stay up late, because at last his work neared its completion.
No more than an hour later, he stood and yawned. Everything was ready for the big demonstration later in the week. Just then, he heard a noise. Intending to lecture his daughter or a pet for unwarranted nocturnal activity, he walked through the house looking for the source only to find his door torn from its hinges and on the ground next to it, a paper wrapped around a key.
"Give up your foolish scheme! You're hurting us all! Including yourself!" He read that and crumpled the message in his angry fist. Determined, he placed the key on his workbench next to his project.
"You fiends," he said, unable to keep his indignant thoughts silent. "Threatening me because of how my invention terrifies you." He compared the two, nodded, and picked up his model. "This key which doesn't disappear when it's used will ruin your Keymakers' Guild!"
Finis