Krrik essentially only costs 4 Mana to cast, by paying 6 life to get Phyrexian Mana
It costs 7 mana to give a single creature islandwalk, so thats a little pricey
Its important to have two lands in play before you go off
And, yeah, judging by the Wilds of Eldraine printing, which was also part of a bonus sheet ( Enchanting Tales ), these are actually the expected prices even well after the set's hype dies down
It's unclear whether this was the most necessary of the Slivers, but it was the one that frustrated the most opposing plans to deal with the problem and even opened up new game plans when the card advantage resulting from saving your creatures could allow Sliver decks to go the control route when backed up by counters and removal spells
In addition to the official reveal of the new Lord of the Rings Scene Boxes, IGN also revealed five new chase cards that will appear in the new wave of Lord of the Rings Collector Boosters