**NOTE – major US-pace spoilers below, do not continue unless you have seen ‘Crisis on Infinite Earths, Part Three’**
In the latest episode, the Arrowverse’s John Constantine (Matt Ryan), accompanied by John Diggle/Spartan (David Ramsey) and Mia Smoak-Queen (Katherine McNamara), seeks out the help of an old acquaintance in order to resurrect Mia’s father, Oliver Queen.
Who is this old friend? None other than the devil himself, Lucifer Morningstar (Tom Ellis), who is stumbling out of his club when confronted by Constantine.
The pair exchange testy greetings before ‘Lucey’ uses his power on Mia to discover that the soul they’re hoping to retrieve is in fact her father’s.
Admitting he owes Constantine a favour, he then offers them a playing card, which proves to be their ticket into purgatory, providing they get out before the picture on the card fades away.
Elsewhere in the scene, eagle-eyed viewers may have spotted an easter egg reference to HBO’s Watchmen (it began as a DC comic series), which could be seen emblazoned on a billboard.