I have noticed that Grog-Gnog’s Strike slows enemies even when debuff immune. I was attacking a Grog-Gnog-Solaris-Igorok-Koros defense team and I used Abigail-Shade-Balog-Drakk. They had there Grog-Gnog attack before there Koros so it’s not like Koros removed the dark shroud buff. The attack went this order my Abigail, my Shade, there Grog-Gnog, there Solaris, my Balog, my Drakk. There Koros and Igorok died before they could attack. All of my hero’s are fully ascended.