Caldaia Guardian — ruling 1

If you choose to pay the blitz cost rather than the mana cost, you're still casting the spell. It goes on the stack and can be responded to and countered. You can cast a creature spell for its blitz cost only if you could cast that creature spell. Most of the time, this means during your main phase when the stack is empty.

Caldaia Guardian — ruling 2

If you pay the blitz cost to cast a creature spell, that permanent will be sacrificed only if it's still on the battlefield when that triggered ability resolves. If it dies or goes to another zone before then, it will stay where it is.

Caldaia Guardian — ruling 3

You don't have to attack with the creature with blitz unless another ability says you do.

Caldaia Guardian — ruling 4

If a creature enters the battlefield as a copy of or becomes a copy of a creature whose blitz cost was paid, the copy won't have haste, won't be sacrificed, and its controller won't draw a card when it dies.

Caldaia Guardian — ruling 5

The triggered ability that lets its controller draw a card triggers when it dies for any reason, not just when you sacrifice it during the end step.

Caldaia Guardian : règles, fonctionnement et interactions (MTG)

Caldaia Guardian 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

Whenever this creature or another creature you control with mana value 4 or greater dies, create two 1/1 green and white Citizen creature tokens. Blitz (If you cast this spell for its blitz cost, it gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step.)

How it works : Caldaia Guardian

Original English text — Wizards of the Coast / Scryfall

#1April 29, 2022· Wizards of the Coast
If you choose to pay the blitz cost rather than the mana cost, you're still casting the spell. It goes on the stack and can be responded to and countered. You can cast a creature spell for its blitz cost only if you could cast that creature spell. Most of the time, this means during your main phase when the stack is empty.
No other card is named in this ruling.
#2April 29, 2022· Wizards of the Coast
If you pay the blitz cost to cast a creature spell, that permanent will be sacrificed only if it's still on the battlefield when that triggered ability resolves. If it dies or goes to another zone before then, it will stay where it is.
No other card is named in this ruling.
#3April 29, 2022· Wizards of the Coast
You don't have to attack with the creature with blitz unless another ability says you do.
No other card is named in this ruling.
#4April 29, 2022· Wizards of the Coast
If a creature enters the battlefield as a copy of or becomes a copy of a creature whose blitz cost was paid, the copy won't have haste, won't be sacrificed, and its controller won't draw a card when it dies.
No other card is named in this ruling.
#5April 29, 2022· Wizards of the Coast
The triggered ability that lets its controller draw a card triggers when it dies for any reason, not just when you sacrifice it during the end step.
No other card is named in this ruling.