When are you introducing a pillow and duvet to your baby?

My girl is 18 months she started using a pillow and duvet at 16 months.
It would be different for every bub tho.
I started to play a “game” with her at 12 months while she was laying down. I would cover her face with the blanket and show her how to get out of it. Now she sleeps with a blanket and I’m not worried at all because I know if she does cover her self while she’s asleep, she knows how to get out of the situation.