Collector Ouphe shuts off activated abilities of artifacts, so it stops their Lotus Petal from being sacrificed for mana. It does nothing against Chalice of the Void, which only has a triggered ability. Doorkeeper Thrull can block their ground creatures and prevents abilities from triggering when artifacts or creatures enter. We cut slower cards that do little against a deck that can counter our cheap spells with Chalice of the Void.