If Tianna prevents scoring points while at a battlefield, and a player attempts to score from holding that battlefield (gaining no points due to Tianna), can they later remove Tianna and score again from conquering that same battlefield on the same turn?

Ruling: No. Tianna prevents points from being scored but does not prevent the actual Scoring of the battlefield. When you hold or conquer while Tianna is active, you Score the battlefield (triggering abilities) but gain no points. Since you already Scored that battlefield this turn, you cannot Score it again even after removing Tianna, as you may only Score once per battlefield per turn.

Sequence:

• Player holds/conquers battlefield while Tianna is active
• Battlefield is Scored (abilities trigger) but no point is awarded
• Player removes Tianna during same turn
• Player cannot Score that battlefield again this turn (already Scored)

Nuances:

• If a player Scores one battlefield while Tianna is active (no point awarded), then removes Tianna and Scores a different battlefield at 7 points, they would gain the 8th victory point since both battlefields have been Scored
• The draw effect at 7 points specifically requires gaining a conquer point, so holding a battlefield at 7 points while Tianna is active does not trigger the draw