I have determined sentry and lonely poro in base, opponent played Bellows Breath repeated in my base, do I draw or not? What is the order of repeat in chain?

To determine whether you draw a card, we must look at the "alone" condition of your Lonely Poro at the moment it dies.

The Ruling: Do you draw a card?

No, you do not draw a card.

According to the Lonely Poro card text, the [Deathknell] ability triggers if the Poro "died alone," meaning there were no other friendly units at its location (the base) at the moment of death. Because you also have a Determined Sentry in your base, the Lonely Poro is not "alone." Even if the Bellows Breath damage kills both units simultaneously, the "alone" condition is checked based on the state of the board at the moment of death. Since the Determined Sentry was present in your base alongside the Poro, the Poro was not alone, and its [Deathknell] will not trigger.

Order of Repeat on the Chain

Regarding how [Repeat] works on the chain, here is the technical breakdown:

1. Playing the Spell: When you pay the [Repeat] cost, you are not creating a second instance of the spell or a second item on the chain. You are simply modifying the existing Bellows Breath spell to execute its instructions a second time when it resolves (Rule 820.1.d).
2. No Multiple Chain Items: There is only one Bellows Breath item on the chain.
3. Resolution: When the spell resolves (Step 4), it executes its instructions in full. Because the Repeat cost was paid, it executes the instruction ("Deal 1 to up to three units at the same location") a first time, and then immediately executes it again as part of the same resolution process (Rule 820.1.d.1).

Summary of Events:

• Bellows Breath is played as a single item on the chain.
• Upon resolution, the first execution of Bellows Breath deals 1 damage to your units in the base.
• If that damage is lethal to both, they both die simultaneously.
• Because the Determined Sentry was present at that location when the Lonely Poro died, the Poro was not alone, failing the [Deathknell] requirement.
• The second execution of the spell's effect then occurs (though at this point, your units are already dead).