The concept of the "Valkyrie" cards is derived from the valkyries of Norse mythology. Like most of Zigfried's cards, the "Valkyrie" cards are named after characters from the opera Der Ring des Nibelungen.
Despite being based on the same mythology, this archetype has no relation to the "Nordic" archetype.
The names of the "Valkyrie" monsters "Erste", "Zweite", and "Dritte" are the German words for "first", "second" and "third", respectively. However, in the anime dub, the second "Valkyrie" is named "Zwei", which means "two"; "Brunhilde" is named after Brynhild. The Continuous Spell Cards that support them are inspired on the three Norns, female figures from the Norse Mythology that rule the fate of the humans, namely Skuld, Verðandi, and Urðr.
TCG Naming issues
There are some issues regarding the archetype's name in the TCG, mostly because it wasn't released in the OCG first. Thus, despite the fact it was not released in Japan, according to recent errata, "Element Valkyrie" and "Valkyrie of the Nordic Ascendant" are not considered "Valkyrie" monsters, and a new archetype condition was introduced to exclude them.
Also, in the French, Italian, Portuguese and Spanish versions, the archetype names contain a hyphen (e.g. French "Valkyrie-") to exclude all cards that have "Valkyria" or "Valkyrian" in their English names that have been released prior to the realization of this archetype in the TCG, including "Dark Valkyria", "Power Angel Valkyria", "Magician's Valkyria" and "Valkyrian Knight". This is necessary because the English "Valkyria" and "Valkyrian" have been translated to the only words for "valkyrie" in these languages. The hyphen is only used in the names of "Valkyrie" monsters in whose cases the hyphenated archetype names function as prefixes, therefore an archetype condition is added to the card text of "Ride of the Valkyries" to include it in the archetype in these languages. These aren't issues with the German names, because translations for "Valkyrie" ("Walküre") and "Valkyria" ("Valkyre") / "Valkyrian" ("Valkyrischer") are sufficiently distinct.
The Deck sticks foremost to the all-or-nothing tactic of using "Ride of the Valkyries" from the anime, to perform an OTK as soon as possible. The first three "Valkyrie" monsters work in tandem to clear the field and enable their ATK-raising effects.
"Brunhilde" is the ace of the monster line-up. Its main role is to punish swarming by increasing its ATK to surprising heights, depending on Deck match-up, as well as giving the other "Valkyrie" monsters immunity to battle destruction. Its immunity against opposing Spell Effects can come in handy against certain troublesome cards or whole decks, for example, "Lair of Darkness", "Lost World" and "Zombie World", as well as generic cards such as "Book of Moon", "Raigeki" and "Sky Striker Maneuver - Afterburners!".
"Mischief of the Time Goddess" is the objectively most dangerous Spell Card their strategy relies on, as it not only gives the player an additional Battle Phase, but it also bypasses the negative effect of "Ride of the Valkyries". Also, it could allow cards like "Where Arf Thou?" and "Into the Void" to be played safely, bypassing the damage or mass-discard effect during the End Phase, while turning "Honest" into a permanent ATK boost. As it skips a whole turn, it is possible to activate Trap Cards shortly after being Set, get 1 additional Normal Summon during Main Phase 2, and reset once per turn effects. "Foolish Burial Goods" is also a good tech option to send this card to the GY so that you can recover it with "Valkyrie Erste".
“Valkyrie Dritte” is the deck’s main searcher as she can add any Valkyrie card to your hand, so some builds run a few copies of “Condemned Witch”, as it can Special Summon her straight from the Deck, granting her search effect, while also being a good search card herself for the "Forbidden" Quick-Play spells. Also, "Valkyrie Sechste" can provide more searcher abilities once Special Summoned, however, its mill effect can be more of a hindrance than a help against many Decks. Furthermore, "Valkyrie Vierte" can help by adding a Normal Spell/Trap card to the hand like "Raigeki", "Monster Reborn", "Final Light", "Apple of Enlightenment" or simply "Ride".
As the deck can still be vulnerable to battle traps like the "Mirror Force" card and its counterparts, a standard option is to tech in cards like "Twin Twisters" and "Hey, Trunade!" to get rid of problematic backrow cards. This Deck doesn’t rely too much on the Extra Deck, as the OTK strategy means the player is trying to finish off the opponent with the “Valkyries” themselves, and as a result "Pot of Extravagance" for extra draw power is a common choice as losing 3-6 extra Deck monsters does not negatively affect the deck.
The three goddesses ("Skuld", "Verdande" and "Urd") can have a supportive role by preemptively banishing dangerous cards the opponent could have drawn, while protecting the "Valkyries" from being targeted and destroyed by opposing effects. This also creates an opportunity for the player to use cards like "Conscription" and "Mind Crush". As a last resort, they can be used to summon "Hamon, Lord of Striking Thunder" or "Dragon Queen of Tragic Endings". As an additional tech, their power can be combined with "Valkyrie Sechste" second effect; by doing so, the player can freely choose what to banish and what to send to the graveyard, giving almost total control over the opponent's deck.
The deck fails in not having a more intricate gameplay, gambling in an all-out strategy in order to finish the game as soon as possible, in a reminiscence of the feared Zigfried's strategy in the anime. The Deck also suffers from several problems that have plagued similar anime-inspired Decks, with most of its cards lacking serious synergy and underwhelming in power level. The Goddess Continuous Spells, while powerful, don't really fit with the rest of the deck's OTK strategy, and are more suited to a longer Duel, where the rest of the Deck's inadequacies become more and more prevalent. Many of its long-term plans are also based on a mill-control type strategy, hopeless in the modern era of Graveyard effects and recursion.
That said, the main line of the Deck can be vulnerable to cards that prevent them from conducting the Battle Phase or attacking, such as "Threatening Roar" or "Battle Fader". Despite the protection given by "Goddess Urd's Verdict", they are still vulnerable to cards like "Quaking Mirror Force", "Drowning Mirror Force", "Floodgate Trap Hole", etc. This fast-paced strategy also renders them vulnerable to cards like "Anti-Spell Fragrance" and "Imperial Order", which can be fatal to the Deck, postponing the activation of key cards such as "Ride of the Valkyries" and "Mischief of the Time Goddess". Indeed, simply negating "Ride" is normally enough to stop the Valkyrie strategy cold.