Mana Tithe is premium disruption: on the turn they chain Desperate Ritual, Seething Song, and Manamorphose into their payoff, they're often stretched thin on mana, so a counter unless they pay {1} can strand Seize the Storm or a key ritual. Relic of Progenitus lets you proactively exile their graveyard of instants and sorceries before they flashback Seize the Storm, shrinking or denying their only maindeck win condition. Clowning Around's token-making is too slow against a deck racing to one explosive turn, so cut it; the lone Guardians' Pledge doesn't help against a deck with almost no real creatures to fight, so it comes out too. Keep your cheap, efficient beaters applying pressure so they're forced to act before they're fully set up.