The Inca series is the last Dark Signer Deck featured in the Yu-Gi-Oh! 5D's anime, used by Rex Goodwin. They somewhat resemble the mythological creatures and artifacts of the Incan civilization and their names usually represent Incan deities. They were released in Absolute Powerforce.
The main focus of the deck is to Synchro Summon out "Sun Dragon Inti" and "Moon Dragon Quilla". These two Synchro Monsters will form a loop, where one dragon revives another when they are destroyed. The main method to do so is using "Ascator, Dawnwalker" and "Supay, Duskwalker", as both of them can Special Summon the appropriate Tuners from the Deck.
Whilst Inca can be a formidable deck, there are many cards that may cause huge problems for Inca. The main problem is cards that banish the Dragons, or return them back to the Extra Deck. For example, cards like "Bottomless Trap Hole" and "D.D. Crow" are able to permanently banish the dragons from the game, thus ending the loop. While "Brionac, Dragon of the Ice Barrier" could return them to the Extra Deck, which means you will have to re-Synchro Summon the Dragons. Another weakness is that the Dragons both require specific Tuner monsters. "Soul Drain" can cripple the Graveyard hindering their effect, and "Necrovalley" shuts their effects down as well.
- Inti and Quilla are most likely paired up and given the ability to revive one another because Inti, the sun god, was married to Mama Quilla, the moon goddess - this is symbolic of the way day chases night, and vice versa. "Earthbound Immortal Wiraqocha Rasca" is also based on Viraqocha, the god of everything in Incan culture.
- Out of all the Incan monsters, Ascator is the only one that isnt based on a figure of Incan mythology, rather its based on Azcatl of Aztec mythology.
- There are many different variants for an Inca deck. For a broader understanding of these variants the following thread is helpful: http://www.pojo.biz/board/showthread.php?t=971899