Panharmonicon reads: 'If an artifact or creature entering the battlefield causes a triggered ability of an artifact or creature you control to trigger, that ability triggers an additional time.' The key question is whether an artifact creature satisfies this condition — and it does, on both counts.
An artifact creature has both the 'artifact' and 'creature' card types simultaneously (CR 205.2a). When Panharmonicon checks if the permanent entering is 'an artifact or creature,' it only needs to be one of those types. An artifact creature qualifies under either category, so the condition is met.
However, this does NOT mean it triggers a third time. Panharmonicon says the ability triggers 'an additional time' — it doubles the trigger count from 1 to 2, regardless of how many types the entering permanent has. The 'or' in Panharmonicon is not additive (CR 207.2, CR 603.1).
Example: You control Panharmonicon and cast Solemn Simulacrum (an artifact creature). Its 'enters the battlefield' ability to search for a basic land triggers once normally, then Panharmonicon causes it to trigger one additional time — so you search for two basic lands total.
This applies as long as the triggered ability belongs to an artifact or creature you control. The entering permanent being an artifact creature simply ensures Panharmonicon's condition is met; it does not stack multiple additional triggers (CR 603.1, CR 205.2a).
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.