This effect is applied also when you cast a spell without paying its mana cost
Way back in 1997, Wizards released their first MTG video game, which was nicknamed Shandalar since it took place in that plane
The uncommon symbol resembles a book, or a shield that is located at the bottom of the card
I won more than one old Vintage tournament that way with nothing in my deck more expensive than Jester's Cap, thanks to turn after turn of card advantage
From Marta Nael and Martina Fackova making four-panel ones, to Colin Boyer and Kieran Yanner making six-panel ones, to Matt Stewart, Livia Prima, Campbell White and Dave Rapoza making their groups of nine, one stands alone
I should mention that its not all doom and gloom