If Paladin Elizabeth Taggerdy is no longer on the battlefield when its battalion ability resolves, use its power as it last existed on the battlefield to determine the value of X.

Although the creature you put onto the battlefield is attacking, it was never declared as an attacking creature. This means that abilities that trigger whenever a creature attacks won’t trigger when it enters the battlefield attacking.

You choose which player, planeswalker, or battle the creature you put onto the battlefield is attacking as it enters the battlefield. It doesn’t have to be attacking the same player, planeswalker, or battle that Paladin Elizabeth Taggerdy is attacking.

Once Paladin Elizabeth Taggerdy’s battalion ability has triggered, it doesn’t matter how many creatures are still attacking when that ability resolves.

The three attacking creatures don’t have to be attacking the same player, planeswalker, or battle.