Creatures and artifacts that tap or you have to pay a cost to use can't be used unless mana abilities. now cards that are activated by coming into play or does not have a physical cost it don't stop like it will stop an icy manipulator but won't stop a banisher priest. hope this helps
I got another question to Underworld Cerberus does he affect Emrakul, the Aeons Torn ability of When Emrakul is put into a graveyard from anywhere, its owner shuffles his or her graveyard into his or her library.Underworld Cerberus ability is Cards in graveyards can't be the targets of spells or abilities
thats why he doesn't stay in you're graveyard thank dredge decks for that being added. Playing cards from the grave has always been popular to get around casting cost but some cards are considered to powerful to get out before meeting the mana cost.
things that don't say target should work things that trigger but don't let you choose a target work just fine its like the cards in the graveyard have shroud but thing like remove all cards in graveyards from the game still work because no targets.