When Whisperwood Elemental’s sacrifice-granted death triggers and Yedora both respond to the same creature(s) dying, you get two different types of returns: Whisperwood-granted triggers manifest the top card(s) of your library as face-down 2/2 creatures, while Yedora’s triggered ability can return the dead nontoken creature itself to the battlefield face down as a Forest land. Because Yedora’s return puts a permanent onto the battlefield that is a land, that event can trigger Zimone’s landfall ability (unless the land wasn’t entering the battlefield, see Ruling [2024-11-08]). Face-down permanents enter face down before they enter the battlefield, so they don’t have enters-the-battlefield triggered/static ability interactions on entry ; when face-down permanents move zones they must be revealed .
Step 1
You activate/resolve Whisperwood Elemental’s sacrifice ability, giving your face-up nontoken creatures the triggered ability 'When this creature dies, manifest the top card of your library' until end of turn (that grant is a temporary effect; see layering if it interacts with other continuous effects) .
Step 2
One or more of those creatures die (are put from the battlefield into a graveyard). Two sets of triggered abilities will trigger for each dead nontoken creature: (A) the Whisperwood-granted 'manifest' triggers controlled by you, and (B) Yedora’s 'Whenever another nontoken creature you control dies, you may return it to the battlefield face down…' triggers controlled by Yedora’s controller. These triggers are put on the stack; if you control multiple triggers, you order them in APNAP order.
Step 3
You choose the order in which those triggers go on the stack (you control both Whisperwood-granted triggers and Yedora triggers if you control both sources). The chosen order determines what resolves first.
Step 4
If a Whisperwood-granted manifest trigger resolves, you manifest the top card of your library (put it onto the battlefield face down as a 2/2 creature). Because objects put onto the battlefield face down are turned face down before they enter, that face-down creature won’t have any enters-the-battlefield triggered or static abilities on entry .
Step 5
If a Yedora trigger resolves and you choose to return the dead nontoken creature, that specific card is returned to the battlefield face down under its owner’s control and 'It’s a Forest land' as specified. That is a permanent entering the battlefield that is a land, so it can cause Zimone’s landfall to trigger (Ruling [2024-11-08] only prevents landfall when something already on the battlefield becomes a land, not when a land enters the battlefield). The face-down permanent’s characteristics are those described in Ruling [2021-04-16].
Step 6
When Yedora’s return puts a face-down Forest onto the battlefield, Zimone’s landfall ability (if Zimone is under your control and the other landfall conditions apply) will trigger because a land entered the battlefield under your control. Zimone’s first resolving landfall that turn will 'manifest dread' (look at top two, put one onto battlefield face down as a 2/2 and the other into the graveyard); if Zimone’s landfall resolves a second time that turn, its second mode lets you 'may turn a permanent you control face up.'
Step 7
If you use Zimone’s 'may turn a permanent you control face up' on the face-down Forest returned by Yedora, you turn that permanent face up and reveal it; because face-down permanents that move zones or are turned face up are revealed, you must show the card underneath . What the face-up result is depends on continuous effects and characteristics that apply after it is face up; note that Ruling [2021-04-16] describes the face-down characteristics Yedora created while it was face down.
Step 8
If the face-down permanent is turned face up and any morph/disguise-type face-up conditions are required, be mindful of Ruling [2024-09-20] which notes that losing an ability used by a face-down mechanic can prevent using that mechanic to turn face up. However, Zimone’s 'turn face up' is an effect that directly turns a permanent face up (not payment of a morph/disguise cost), so it can turn face-down permanents face up even if they no longer have morph/disguise abilities — you will reveal the underlying card when you turn it face up .
Step 9
Throughout, if a face-down permanent leaves the battlefield you must reveal it as it moves zones (for example, if a Yedora-returned face-down Forest later dies) [707.9; 2014-11-24].
Resolution
If you sacrifice Whisperwood to grant death triggers and then one or more of your face-up nontoken creatures die: for each dying creature you’ll get a Whisperwood-granted triggered ability that manifests the top card of your library, and for each dying nontoken creature you’ll get a Yedora triggered ability that may return that creature to the battlefield face down as a Forest land. The controller of those triggered abilities chooses their stack order (APNAP ordering for simultaneous triggers they control). If Yedora’s trigger resolves and returns the card to the battlefield face down, that object enters the battlefield as a land and can cause Zimone’s landfall to trigger (Zimone’s landfall triggers when a land enters, and Ruling [2024-11-08] only prevents landfall when an already-on-battlefield permanent becomes a land). The Whisperwood manifests create face-down 2/2 creatures; Yedora’s returns create face-down Forest lands whose face-down characteristics are described in Ruling [2021-04-16]. Face-down permanents are turned face down before they enter, so their ETB abilities won’t trigger on entry , and if a face-down permanent later moves zones you must reveal it .
