At the beginning of your end step, Jon Irenicus triggers, giving control of Sea Serpent to an opponent who controls no Islands.
When Sea Serpent's controller controls no Islands, Sea Serpent triggers, causing them to sacrifice it.
However, Sea Serpent cannot be sacrificed due to its ability.
Sea Serpent triggers again, creating a mandatory infinite loop that causes the game to end in a draw.

Draw the game

Jon Irenicus, Shattered One

Sea Serpent

If needed, give control of Sea Serpent to an opponent who controls no Islands.
When Sea Serpent's controller controls no Islands, Sea Serpent triggers, causing them to sacrifice it.
However, Sea Serpent cannot be sacrificed due to Assault Suit.
Sea Serpent triggers again, creating a mandatory infinite loop that causes the game to end in a draw.

Combos with "Sea Serpent"