Making your Creatures hard to block and preventing damage dealt by those blockers is a juicy combination
Sort of like with multicolored and legendary cards, their execution wasnt very good
You'll see a collector number followed by a single letter: C, U, R, or M
309.2d: If an effect other than a venture into the dungeon keyword action would bring a dungeon card into the game from outside the game, it doesnt
Dont be afraid to slam this on curve as a way to accelerate, though, as the card advantage isnt what makes this card good its just gravy
So they can be reduced by Ugin, the Ineffable, countered by cards like Counterspell and Essence Scatter, and also trigger abilities like Animar, Soul of Elements and Beast Whisperer