Steam is offering Minion Masters Accursed Army Pack DLC for free. Normally $18.49. You must have the free-to-play base game first. Just click Play Game and it'll be added to your library. Then you can get the Accursed Army Pack for free. To keep them forever you must claim before May 31st.
Minion Masters is rated Very Positive from 15,357 reviews. Both game and DLC include Steam trading cards.
Also available on the Microsoft Store.