Amy The Pixie

[Thanatos The Lord Of Chaos]

Amy The Pixie . " Super Rare " 

Level . 5

Attribute. Dark/Fire 

Type . Fairy 

ATK . 1300

DEF . 1000

Effect . This card is also considered to be a " Fire " attribute monster .This card must be Special summoned  ( From your hand) by banishing 1 " Dark " Attribute normal monster from your opponents graveyard and 1 " Fire " Attribute effect monster from your extra deck . When this card is destroyed you must Special summon 1 level 8 or higher "Fairy" type Synchro monster ignoring summoning conditions from either players extra decks

[Darj]

There is no such thing as a printed dual-Attribute monster. You can add extra Attributes by effects, as you already did with the "treated as FIRE" effect. Text fix.
(This card is also always treated as a FIRE monster)
Cannot be Normal Summoned/Set. Must be Special Summoned (from your hand) by banishing 1 DARK Normal Monster from your opponent's GY and 1 FIRE Effect Monster from your Extra Deck. When this card is destroyed: Special Summon 1 Level 8 or higher Fairy Synchro monster form either player's Extra Deck, ignoring its summoning conditions.

Now, this is a rather unorthodox card. It banishes from the opponent's GY for its Summon, something that so far no official card does, but I see no problem with that, card making is for exploring different things and breaking out of the mold, after all. Then the float into a Synchro feel kinda random but should still be fine. My only concern is that by mechanics you would get to take a peek at the opponent's Extra Deck to check for any Fairy Synchro you could Summon if you suspect they have any, even if they don't, and that's intel for you, which is deceptively good because then you get to see what to expect from the opponent's Extra Deck.
Anyway, the effect is potent because then you can Summon stuff as big as Odin, Father of the Aesir, but the bottleneck is Summoning this card since it is match-up dependent, as it requires your opponent to be running DARK Normal monsters in the first place, and decks that run them are scarce. I can only think of Evilswarms, which have been out of relevancy for a couple of years now, and Dragon variants with Labradorite Dragon, which also have not seen a lot of play lately but that may change with the new Master Rule 2020 and Needlefiber/Halqifibrax coming to the TCG, who knows. In short, the card is not bad per se, but highly situational and match-up dependent.