🧩 Riddle of the Day 🧠

I am sometimes full of keys but never open a door.

🧠 Proof of Brain (4 HOURS) ⏳

⚡ 5 sats: 👀 Sneak peek — how long's the answer?
⚡ 10 sats: 🕵️‍♂️ First letter? Fine, take it.
⚡ 22 sats: 💀 Reveal all. The riddle dies, you win (kinda).