Does Star Cross on Brynhir Thundersong prevent the Bryn effect?
No, playing Star-Crossed to return Brynhir Thundersong to your hand does not prevent her "When you play me" triggered ability from resolving.
According to the rules of Riftbound and RiftJudge FAQ #10679:
- Ability Independence: Once a triggered ability (like Brynhir Thundersong's "When you play me" effect) has been placed on the chain, it becomes independent of the unit that created it.
- Resolution: The game follows a Last-In, First-Out (LIFO) resolution order. If you play Brynhir Thundersong and your opponent reacts with Star-Crossed, Star-Crossed resolves first, returning Brynhir to your hand. However, her triggered ability remains on the chain and will still resolve immediately afterward, preventing your opponent from playing cards for the remainder of the turn.
As stated in the FAQ: "Once the triggered ability is on the chain, it is independent of the unit that created it... it will execute its effects regardless of whether the unit is still in play, provided the ability's instructions can still be followed."