Both protagonists and villains had another problem to face.
Because Chrysalis was gossiping everywhere in different disguises, causing discords and emnity between earth ponies, unicorns and pegasi, as well as other non-pony creatures with Tirek helping her by destroying crops and making even more mess to make ponies believe it's specific pony type's fault, a mythical creatures have been summoned - Windigos. The same creatures mentioned each year during Heart's Warming Eve, who nearly made Equestria icy, lifeless desert.
"Are these...Windigos?" - Chrysalis asked surprised, staring at white, glowing dragon-shaped creatures flying in circle - "I didn't know they were real"
"Looks like they are and it only confirms our plan to set ponies at variance was successful" - Tirek exclaimed with evil grin
"So, if Windigos have been summoned, that means there is a lot of emnity between creatures. We are still strong, even when Twilight and the others are free" - he confirmed.
"They must be hiding in Ponyville's castle of friendship, let's get there!" - Chrysalis commanded
Soon after, Tirek and Chrysalis were standing in front of the Ponyville's castle
"Let's get in, shall we?" - Chrysalis said
"Let's go!" - Tirek replied and punched doors at the main entrance of the castle to break in, making them break out of hinges.
Chrysalis got inside first and Tirek followed her. Unfortunately for him, his size made it impossible for him to enter. He tried to wreck the wall to enter, but no avail.
"Chrysalis, you have to check here alone. I'm too large, but I can keep guard here" - he said
Chrysalis growled and sighed, not happy with having to check this place by herself. But she realised one thing - she had so much power, that she can use a spell to scan the entire place.
"Wait, I can scan this place to look for other living creatures" - she said, but there was another flaw - "all I need is that book we used on Discord to take his magic."
"UGH!" - Tirek sighed - "We have to go back to our hideout for it"
"Alright. Let's get this done" - Chrysalis said while flying out the castle and heading to Grogar's Lair
They got to their hideout 5 minutes later. Chrysalis got inside and grabbed the book with her magic.
"I have the book, now let's find the right spell..." - she thought, gasping at the mark of ripped off pages, where the spells for Bewitching Bell were.
"Wait! Something is not right..." - she exclaimed as she flew out the lair
"What is it Chrysalis?" - he asked, wondering what went wrong this time
"Some pages are missing. Two sheets were ripped off this book and it seems they were spells to activate Grogar's Bell" - Chrysalis explained
"You see, Chrysalis" - he began - "It was Cozy Glow - she had trouble casting the spell wihtout looking at the book, so I let her get the pages from book" - Tirek explained what happened to this book
"So she has sheets of paper, but we have an actual item - they were fools to not hide it" - Chrysalis said, but gasped when she realised one thing - "I don't remember this spell. What about you, Tirek?"
"No. I also was looking at the book when I cast the spell for empowering us" - he replied, but another vicious plan came to his mind and added - "Well - plan B"
"What do you mean? What 'plan B'"? - she asked, wondering what Tirek is up to.
"Give me that book!" - he took it from Chrysalis' magic grip - "It must be somewhere...maybe here..." - he muttered to himself
"Tirek, what are you..." - Chrysalis asked a bit annoyed, but Tirek cut her off, putting his palm near Chrysalis muzzle
"Shhhh! I'm looking for one thing...YES! There it is" - he shouted
"What? What did you find?" - she asked startled
"Let me explain you my 'plan B' - I will open the Limbo and get out Pony of Shadows and other creatures like that and bring back King Sombra" - he told
"Well...we don't have any better option, do we? I mean, King Sombra wanted to fight alone, and I doubt he'd do it this time" - Chrysalis was a bit unsure
"We have to do it" - he replied. Chrysalis just nodded.
"Are you sure you know what you are doing?" - Chrysalis was a bit concerned
"I am" - he reassured - "we have enough power to open the portal to underworld to get King Sombra back and open Limbo - there also must be some creatures except Pony of Shadows that will help us"
After that being said, Tirek and Chrysalis used their magic and cumulated it in one spot in the air. Then Tirek shot magical blast to floating orb as a final step.
This caused the Limbo to open once again and let Pony of Shadows get out of there. Without his host - Stygian - his power was significantly weaker than before being banished to Limbo because he lost his host. Therefore, he was a size of average pony.
Also another creatures fleed the Limbo. These were 3 dragon-like individuals called Sirens. They were able of singing special song that drives ponies insane.
The rescued creatures hit the ground with a thud. First one to notice Tirek and Chrysalis was Pony of Shadows.
"Who...are you?" - he asked with voice that suggested he is weakened
"I'm Lord Tirek" - he introduced himself and soon his companion - "and this is Queen Chrysalis".
"We will need you to fight by out side with Twilight and her allies" - Chrysalis explained what they are up to
"I'm in! They made me weak and banished me to Limbo. I will show them who I am!" - he exclaimed
"And so we are" - spoke bluish Siren, making Pony of Shadows, Tirek and Chrysalis a little surprised, since they didn't know Sirens were able to talk.
Now it was the time to bring back King Sombra. Tirek knew how to cast a spell like that. He did exactly the same what "Grogar" did, when he respawned him the day he gathered the most dangerous villains from Equestria.
So he grabbed a stick, casted a spell on it to give it proper ability, the draw a cirkle with border of special pattern on the ground, then put the horizonal line* in the middle of it and finally drew "M" letter in it, hoping that this spell will work and respawn King Sombra, since this spell used most of his magic durability.
It worked - a black crystal appeared on the circle's middle and released dark and dense smoke. Soon, he was summoned - King Sombra, who was dumbfounded - is he still alive despite the fact he got wiped out? Wasn't he defeated by Twilight and her friends at Crystal Empire Castle?
"You again?" - King Sombra asked confused, pointing his forehoof at them
"Yes, but this time you must work with us to finally get rid of Twilight Sparkle!" - Chrysalis commanded, remembering his failure
"Ugh. Fine. Seems I don't have any option. But where's Grogar?" - he replied.
"It wasn't real Grogar. It was Discord in disguise" - Chrysalis amended
"Alright! Now, since we must work together to defeat the most powerful ponies and this Draconequus, we need a plan how to strike!" - Tirek said, trying to make every creature focus on their main goal.
30 minutes later, the expanded squad of villains were done making the plan. What's more interesting, King Sombra had many smart ideas how and where to strike.
"Okay, so everyone knows what each one has to do?" - Chrysalis asked. Everyone nodded and Sirens confirmed by saying "yeah" in unison.
"Let's get this done already, okay?" - Pony of Shadows exclaimed
"Wait!" - Tirek shouted - "just one more thing before we go to battleground..." - Tirek said when red orb of magic appeared between his horns.
"Wait, what are you going to do, Tirek?" - King Sombra asked
"You need more power to face Twilight and her allies" - he replies - "so, I will give you some magic taken from Pillars"
After that, he released some magic streams and shot them to King Sombra, Pony of Shadows and Sirens. They all felt sudden power increase, making Pony of Shadows go back to his original size and Sombra to be able to cast spells.
"Alright, let's go! We have Equestria to conquer!" - Chrysalis commanded and the group left their hideout to fight main protectors of Equestria.