If Tianna Crownguard prevents me from gaining a holding point at a battlefield, then I kill Tianna and re-enter that battlefield with a different unit, do I score a conquest point?

Ruling: No, you do not score a conquest point. Even though Tianna prevents you from gaining the point, the battlefield is still considered "Scored" for the turn when you attempt to Hold it.

Sequence:

• At the start of your turn, you attempt to Hold the battlefield (initiating the Scoring process)
• Tianna's ability prevents you from gaining the point, but the act of Scoring still occurs
• The battlefield is now marked as Scored for this turn, even though no point was gained
• Later when you move a unit back into the battlefield, you cannot Conquer it because you already Scored that battlefield this turn
• You can only Score each battlefield once per turn, regardless of whether a point was actually gained

Nuances:

• Tianna's errata clarifies she prevents gaining points, not the act of Scoring itself
• The Scoring process has two parts: earning a point and triggering Score abilities - Tianna only prevents the first part
• If you had never attempted to Hold (e.g., had no unit there at the start of turn), then killing Tianna and entering would allow a Conquest