Neutral.
Event. Cost: 1.

Dream.

Action: Choose a character or location. Until the end of the phase, treat that card's printed text box as if it were blank (except for Traits).

Yet in his nightmare he faced it again...
Jeremy Wilson
Calm over Westeros #99.

Link: Decklists

Nightmares
Reviews

Rules FAQ

"When the phase ends" interrupt abilities are triggered before "Until the end of the phase" lasting effects wear off, so Nightmares will blank The Reed Keep, The Wall, etc. for, essentially, the entire phase.

"Until the end of the phase" lasting effects wear off before "At the end of the phase" delayed effects trigger, so if you blank Benjen Stark and kill him with Tears of Lys, Benjen's opponent can still trigger his ability (same goes for Ser Davos Seaworth, Joffrey Baratheon, etc.)