Ryvura

This is how The Overlord reveals himself as the leader of the Sons of Garmadon goes in Game of Masks.

Twilight Sparkle: Who was that guy?

Killow: Oh, that's right. You haven't been formally introduced to our leader. [to his leader] Boss, come say hi to the kids.

Applejack: What the hat?

[The leader comes over]

RYAN '''Mr. E: After we were ?????, we needed someone to lead. Luckily, we found a ??? who believed in us. Say hello to our ?????, ?????, and all-time ?????, the Quiet One.'''

Applejack: Why's he wearing a helmet?

[The Quiet One takes off his helmet and reveals himself as the Overlord with disfigured scars on the right side of his face]

Applejack: Ugh.

Rarity: What?

Ultra Violet: Man, we have got to get you into a dermatologist.

[The Overlord looks at her and back at the heroes]

RYAN Twilight Sparkle: ?????

The Overlord: You alicorns are no longer the only ones with alicorn magic.

Killow: The Overlord agreed to lead us so long as we shared power with him.

Mr. E: He implants every type of magic to make himself more powerful.