What is the status of cards that are under other cards? Can you destroy them?
For example, will Omni-X's Singularity or Self-Sabotage allow him to use components that are under La Capitan or Pterodactyl Thief?
My gut answer is "No" as they're not in play to actually destroy. That said, if say Haka's Savage Mana gets destroyed, all the cards under it return to their owner's trash piles.
It depends on the cards actually. If something says "destroy a hero card" it is able to destroy cards located underneath something, but if it gets specific like "destroy a hero ongoing" it will no longer be able to destroy it. Unless the card which holds cards underneath it say they are not considered in play. The reason behind this is cards are considered to have a blank front when under other cards, but they still retain their back, thus keeping their hero/villain/environment card status, along with the hero they belong to. Freedom 6 Tempest can use Sacrifice to destroy one of his cards that are located under La Capitan.
I'll point out that the only confirmed one to work is Freedom 6 Tempest with La Capitan, everything else is what I had expanded on myself, as it makes sense to me. I apologize in advance if it ever comes up that F6 Tempest is the only special case and it wasn't meant to work for anything else.
I believe you could not destroy cards under another card for Singularity or Self-Sabotage, because cards under other cards lose their text, and are only counted as cards, not Equipment or Components.
That's why F6 Tempest works, it only has to be one of your cards, it doesn't have to have text.