Astrid

Astrid took one look around the room then suddenly she heard Kuro call for backup. She then looked over to Raiden and said,

"We'll leave this to you, seeing as you can read ruins. Me, Blade and the twins will go back up Kuro."

With that Astrid grabbed Blade and grew ice wings as she flew back up the hole. She raced to Kuro's location flying as fast as her wings would carry her. She arrived within few minutes with Blade. She then let go of Blade and dropping him on his head as she got ready to help fight that monstrous dragon should he wake up.

Raiden

As Raiden walked up to the alter, he was looking at all the runes along the walls and floor, most were unreadable due to their age, he could only make out bits and pieces. As he got to the center of the room he saw another rune, at this point it was obvious these runes were for a transportation spell. The scary thing was that means somebody has the ability to teleport in and out of Berk at any time. Raiden then decided to grab the note book. He then used his DNA manipulation to give himself the roar of a thunderdrum and the wings of a nightfurry. He then walked over to the exit as he used the roar of the thunderdrum. All the runes began to crack and crumble and the cave began to collapse. Raiden then flew out of the hole as he had a look at the notebook and quickly read through it as he flew over to Kuro. 

The Twins

As soon as the twins had got to the secret room they heard a message from Kuro telling them about a huge dragon, they looked to each other and at the same time they shouted, 'Awesome' then both grew bone wings and flew out the hole towards Kuro before Astrid even gave them the order.