@Setsugekka  

 
You would mean Mommy Storm Monster who wants to get her Little Storm Monster back from both Rusty and the Timberwolf.

That lightning strike better be Tempest whose somehow suspected that Lullaby is missing and came to her rescue right after we see some flashback pages of Tempest with the Fizzlepop doll, while having a conflict with the evil Thunderstone orb within her for Tempest to set things right.
 
Tempest will possibly ditch her restored horn which it was made from the evil orb, return to Thistle and mend their relationship, rescue Lullaby together after discovering she’s missing thanks to Rusty with Fireweed on their side for him to make up for his own mistake of unintentionally dooming Equestria with the Thunderstone and finally put his own cousin Rusty in his place and finally accept Tempest as a friend and possible sister in law.

The Storm Monster has arrived. Now let’s see who is more scary!

Ooh, birch timberwolf. You don’t see a lot of variety there.