Panharmonicon causes each enters-the-battlefield triggered ability caused by a creature entering to trigger an additional time, so Peregrine Drake's “When this creature enters, untap up to five lands.” will trigger twice when it enters, and Venser, Shaper Savant's “When Venser enters, return target spell or permanent to its owner's hand.” will trigger twice when it enters . The Drake untap triggers don’t target and will each resolve and untap up to five lands even if the Drake is later bounced before those triggers resolve (see also Ruling [2022-12-08]). Venser’s doubled triggers are targeted; you choose targets when each trigger is put on the stack, and if one Venser trigger returns a permanent (for example Peregrine Drake) to hand, the other Venser trigger may later resolve but will do nothing if the targeted object is no longer in the zone the ability expects to act on .
Step 1
Peregrine Drake enters the battlefield; this creates an enters-the-battlefield event and Drake’s ETB trigger is identified and placed on the stack. Panharmonicon causes that trigger to be placed on the stack an additional time when a creature entering caused it to trigger .
Step 2
Each Peregrine Drake ETB trigger is a triggered ability that untaps up to five lands. These triggered abilities don’t target; you choose which lands to untap as each ability resolves (Ruling [2022-12-08]).
Step 3
If you flash Venser in (or Venser otherwise enters), Venser’s enters-the-battlefield trigger(s) are identified. Panharmonicon causes Venser’s ETB to be placed on the stack an additional time as well because a creature entering caused a triggered ability of a permanent you control to trigger .
Step 4
When each Venser trigger is put on the stack you choose targets for that triggered ability. Each trigger is a separate object on the stack and can target the same or different spells/permanents.
Step 5
When a Venser trigger resolves it attempts to return the targeted spell or permanent to its owner’s hand. If the targeted object is no longer in the zone the effect expects (for example, the first Venser trigger already returned the permanent to hand), the later Venser trigger will attempt to return it but will do nothing if it cannot find the object in the expected zone .
Step 6
Drake’s untap triggers will still resolve and untap lands even if Drake was returned to hand by a Venser trigger earlier, because the Drake untap triggers don’t depend on Drake remaining on the battlefield (see also ).
Resolution
When Peregrine Drake enters the battlefield under your control with Panharmonicon also under your control, Drake’s ETB ability will be placed on the stack twice and each copy will resolve and can untap up to five lands (they are not targeted) (Ruling [2022-12-08]). When Venser enters with Panharmonicon in play, Venser’s ETB ability will be placed on the stack twice; you choose targets for each triggered ability as they are put on the stack. If both Venser triggers target the same permanent (for example, Peregrine Drake), the first to resolve can return that permanent to its owner’s hand; the second trigger will then attempt to return that same object but will do nothing if the object is no longer in the expected zone when the ability resolves . Replacement effects that modify how a permanent enters the battlefield aren’t duplicated by Panharmonicon (Ruling [2021-03-19]). If Venser’s trigger targets a spell with flashback, it will be exiled instead of returned to hand (Ruling [2017-03-14]).
