What does 'activate' gem means

Necromancer’s ultimate spell creates special gems on a board. I have no clue what to do with them.
Spell description says it will create several sculls when ‘activated’. What does activate means? How do I do it?

necro gems are oddballs… you have to double-click/tap each. When tapped out they will disappear and some skulls (2-4) will be created on the board.

I wish it was in the spell description you can look at in your spell inventory.
I noticed now if you tap any gem once there is a pop up above playing board describing the gem. But I stopped reading them after some time and that’s the only place it tells you to tap second time to activate.

1 Like

Ya. My first hero was a necromancer and I remember being a little confused with the ultimate at first. It’s not exactly clearly explained. I’m sure the various instructions will be more robust when the game is officially released.