Use "Super Double Summon" to Normal Summon "Dark Valkyria" again, and have it gain its effect, use it, and then have it returned it to your hand. This allows yourself to Summon it next turn, with a view to re-using its effect later on.
Since this card is treated as a Normal Monster while in the Graveyard, "Swing of Memories" can be used to Special Summon her from the Graveyard, and then use your Normal Summon to give it it's effect.
This card can make a great combo with "Tempest Magician". Since "Tempest Magician" can place Spell Counters at the cost of discarding cards, they can be placed on the effect of "Dark Valkyria" to boost her attack or clear the field.
Since this card is Level 4 and DARK it is very effective when used with "Shadow Delver", especially if it power up with "Pitch-Black Power Stone" or "Tempest Magician" before an attack.
With "Tempest Magician", "Magical Thorn" and "Forced Requisition" in play and discarding four cards, around 8300 damage can be deal by pumping "Valkyria" with the effect of "Tempest Magician" (triggering "Forced Requisition" and "Magical Thorn"), using "Delver" to attack directly with her, and then using the counters with the burn effect of "Tempest Magician". Though it has many parts, this is an OTK.
With "Athena" and "Dark Valkyria" on the field, "Dark Valkyria" can be send to the Graveyard and return it each turn, allowing yourself to reuse her effect and do 1200 damage per turn: 600 from Summoning "Dark Valkyria" from the Graveyard and 600 from Gemini Summoning her, in addition to providing constant attack power and monster destruction.
With "Summoner Monk" on the field, this card can be Special Summoned and re-Summon to use its effects, plus if "Magical Citadel of Endymion" is on the field, the Spell Counters that were saved for "Endymion, The Master Magician" can be used by "Dark Valkyria" and destroy multiple enemies in one turn, because the effect of "Dark Valkyria"t can be used multiple times per turn.
With "Supervise" and "Giant Trunade" in hand, this card's effect can be reused in the same turn and attack without worrying about Traps. Simply summon "Dark Valkyria", equip "Supervise", use her effect, cast "Giant Trunade" which will return "Supervise" to your hand, equip it again, and use her effect again.