Arriving at the museum/Finding a Painting of the First Spinjitzu Master and the Overlord

Here is how the painting of the First Spinjitzu Master and the Overlord was found in The Overlord's Revenge.

Soon, everyone and everypony arrived at the museum to explore the museum culture.

SpongeBob SquarePants: Wow! We're actually here at the new Ninjago section of the museum.

Patrick Star: Everything is awesome!

SpongeBob SquarePants: Cool! (they see the Sword of Sanctuary) The Sword of Sanctuary!

Patrick Star: Touch.

Guard: Don't touch.

Then, SpongeBob and Patrick walk up to the Realm Crystal.

SpongeBob SquarePants: Wow! The Realm Crystal!

Patrick Star: Touch.

Guard: Don't touch!

Later, they discovered the Time Blades.

SpongeBob SquarePants: Look! It's the new replicas of the Time Blades Stygian created!

Patrick Star: Touch.

Guard: Do I have to follow you all day?!

Sid: Hey, guys. Look what I found.

So, everyone and everypony else came to look at what Sid found.

As they look, Sid was showing a painting of some sort. It was the First Spinjitzu Master during his last battle with the Overlord.

Emmet Brickowski: Uh, isn't that the First Spinjitzu Master?

Wyldstyle: I think so. (realized as she looked at Lloyd) Lloyd, it's your grandfather.

Lloyd Garmadon: Yeah, Wyldstyle. It is my grandfather.

Crane: Anyone recognize this battle?

X-PO: P.I.X.A.L., see if you can scan for observation.

With that said, P.I.X.A.L. detected the history battle between the First Spinjitzu Master and the Overlord.

P.I.X.A.L.: Facial recognition indicates this battle takes place many years ago, during the Stone Wars.

Buck: During the Stone Wars? That was when the Overlord first appeared from some dark thingy.

Twilight Sparkle: That's the darkness, Buck.

Then, Buck sees a black and purple shadowy figure battling the First Spinjitzu Master.

Buck: Who was that battling the First Spinjitzu Master?

SpongeBob SquarePants: It's the Overlord!

Patrick Star: (notice the Giant Stone Warrior mascot and gasped) Oh my gosh! Rocky Stone Warrior! Wait, Rocky! I have to touch you!

Guard #1: (chasing Patrick) Hey!

Batman: What is this? (pointing at the painting of the Overlord)

Guard #2: That's the First Spinjitzu Master and the Overlord in their final battle.

Gandalf: Why is so special about this painting, and why is it here?

Guard #2: Because it shows how the First Spinjitzu Master sacrificed himself to defeat the Overlord by splitting Ninjago in two. But since the two islands are together and with the Overlord and his evil followers in Tartarus, peace has been restored by you guys.

SpongeBob SquarePants: I sure wish the First Spinjitzu Master would be here right now. That would be so cool.

With any doubts, Lloyd could imagine the same thing he imagined.