OCG Rulings

• Discarding one card is an activation cost for the effect which Special Summons it.^[1]

• You cannot activate its effect which Special Summons it during the Damage Step.^[1]

• When you Normal or Special Summon "Chaos Hunter", the effect "Your opponent cannot remove cards from play." is applied, so the opponent cannot activate "Bottomless Trap Hole".^[2]

• If both "Macro Cosmos" and "Chaos Hunter" are both on the field, then you apply the "Your opponent cannot banish cards." effect of "Chaos Hunter". If you control "Chaos Hunter", then your opponent's cards are not banished and are sent to the Graveyard.^[3]

References

1. ↑ ^{1.0 1.1} Konami OCG FAQ: Effect Monster > Chaos Hunter
2. ↑ Konami OCG FAQ: Can your opponent activate "Bottomless Trap Hole" when you Summon "Chaos Hunter"?
3. ↑ Konami OCG FAQ: Is the effect of "Chaos Hunter" applied if "Macro Cosmos" is active?