You cannot activate its effect which Special Summons it during the Damage Step.
If you control "Chaos Hunter", since the "Your opponent cannot banish cards." effect is applied, even if your opponent controls "Macro Cosmos", no cards are banished. (Cards are sent to the Graveyard as usual.) If you control both "Chaos Hunter" and "Macro Cosmos", since it is not your opponent’s card effect, cards are banished as usual. (Both player's cards are banished.)