If the Turn Player declares intent to leave his Main Phase and the opponent activates an effect/card, after the chain resolves, the Turn Player can activate any card he/she can legally activate during that phase. The Turn Player is not required to continue ending the Main Phase.
If a player declares his intent to leave his Main Phase and the opponent activates a card/effect. Once the chain resolves, the Turn Player may continue performing any action he/she can legally perform during that Phase. He/she is not required to continue ending that Phase.
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