Does Brynhir's ability go on the chain, and can reactions be played in response before it resolves?

Ruling: Yes, Brynhir's ability creates a chain from the "When you play me" trigger that you may react to. Once that chain resolves, you are no longer able to play cards.

Sequence:

• Brynhir's "When you play me" trigger goes on the chain
• Players may play reactions in response to this chain
• When the chain resolves, players become shut off from playing cards

Nuances:

• Hidden cards are blocked by this ability because you are "playing" them from hidden, not just "flipping" them
• Hidden cards can still be played if they are in reaction to Brynhir's chain before it resolves