Can you play Rengar, Trophy Hunter to an occupied enemy battlefield with the trigger of Dazzling Aurora?

Yes, if Dazzling Aurora's end-of-turn triggered ability plays Rengar, Trophy Hunter, you can play him to an enemy-occupied battlefield.

According to RiftJudge FAQ #11132, which provides the official ruling on this interaction:

The Reasoning

1. Dazzling Aurora's Trigger: Dazzling Aurora's ability is a triggered ability that plays a unit. When this ability resolves, it provides the instruction to "play" that unit.
2. Playing from Hidden: When an effect instructs you to "play" a card, you must go through the standard process of Playing a Card (Rule 349).
3. Rengar's Unique Permission: Rengar, Trophy Hunter has a specific, unique permission: "I can be played to a battlefield where there are enemy units, even if you don't have units there."
4. Legal Destination: Because Dazzling Aurora instructs you to play the unit, and Rengar provides a valid permission to be played at a battlefield with enemy units, the destination is legal. This is an application of Rule 822.3.a, which notes that "Other effects and permissions may still enable this Unit to be able to be played to the selected location."

Important Timing and State Notes

• Reaction Timing: Because an effect is playing Rengar, the action is performed as part of the resolution of Dazzling Aurora's ability.
• Attacker/Defender Status: Per the rules for contested battlefields (Rule 442.1.a), if you use Dazzling Aurora to play Rengar into a battlefield that is currently contested by your opponent, you will be designated as the Defender.

Summary: You may play Rengar, Trophy Hunter to an enemy-occupied battlefield using Dazzling Aurora’s trigger. This is a legal play because Rengar explicitly grants himself the permission to enter such a location, and the effect provides the necessary instruction to play him.