I'm actually starting to get into DnD and I may be soon buy the DnD starter set. Mimic is a monster whose concept I love, and I would like to put at least one as soon as possible when I'll DM, even if I have to change some little things in the base scenario. But as I never DM'd or even played a DnD game, I don't have any idea on at what level can a party fight one of these monsters with a bit of a challenge but without risking everyone dies.
Based on played games (as DM or player), when should I introduce my first mimic to give my party not too deadly challenge ? (not in term of scenario, but in level meaning)
For more context, my party should be about 4/5 players who're medium used to RP but never played DnD before.