Ambulatory Edifice — ruling 1

You don't choose a target for Ambulatory Edifice's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you pay 2 life this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.

Ambulatory Edifice : règles, fonctionnement et interactions (MTG)

Ambulatory Edifice is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When this creature enters, you may pay 2 life. When you do, target creature gets -1/-1 until end of turn.

How it works : Ambulatory Edifice

Original English text — Wizards of the Coast / Scryfall

#1February 4, 2023· Wizards of the Coast
You don't choose a target for Ambulatory Edifice's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you pay 2 life this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.
No other card is named in this ruling.