Just for fun, I believe there will be 3 dual sphere cards in each sphere: let us see what we have so far, Temple of the Deceived and future cycle spoilers included.

Leadership with Tactics

Leadership with Spirit - Ceorl (ally)

Leadership with Lore - Eldahir (ally)

Tactics with Leadership - Deorwine (ally)

Tactics with Spirit

Tactics with Lore - Knife-work (event)

Spirit with Leadership - Inspiring Presence (event)

Spirit with Tactics - Tides of Fate (event)

Spirit with Lore

Lore with Leadership

Lore with Tactics - Arrows from the Trees (event)

Lore with Spirit - Robin Smallburrow (ally)

If the theory is right, one for each sphere remains (both as the main sphere and the supporting). Or have I missed some?

Lore with Leadership is Heed the Dream.

And it's not a theory, it was confirmed somewhere that we're getting all the possible combinations - including each sphere combining with itself, which obviously isn't dual-sphere then but it follows the same principle of having a secondary effect for spending resources as a group. So getting into those as well:

Leadership/Leadership - Dwarven Sellsword (ally)

Tactics/Tactics - Azain Silverbeard (ally)

Spirit/Spirit - Sam Gamgee (ally)

Lore/Lore

Lore with Leadership has "Heed the Dream" from the first AP

Tactics with Tactics has "Azain Silverbeard" from the first AP

Leadership with Leadership has "Dwarven Sellsword" spoiled from the 4th AP

Lore/Lore

Ioreth

How could I forget Heed the Dream, having played the card for a few weeks now. And I was almost going to mention the secondary in-sphere payments but it would not fit into the title, haha. Yes, we have seen them all then… and only 3 dual ones remaining. Leadership with Tactics should be a Gondor (theme) card; Tactics with Spirit might be Rohan; and Spirit with Lore Noldor?