Tilla Mook with "Vampire Lady" (upper left) and "Vampire's Curse" (bottom right)
"Vampire" (ヴァンパイア Vanpaia) is an archetype of DARK Zombie-Type monsters, except the Warrior "Vampire Hunter". Initially, they were only supported by the manga-only card "Blood Curse" and the manga effect of "Overpowering Eye", but Shadow Specters revealed new "Vampire" support.
The original name of "Vampire Orchis" and "Vampire Koala" are 「-ブラッド・オーキス-」 (Blood Orchis) and 「きゅうけつコアラ」 (Bloodsucking Koala) respectively (and their Attributes are EARTH, not DARK), so they are both excluded from cards that support "Vampire" monsters.
In Shadow Specters, the archetype is supported by the Field Spell Card "Vampire Kingdom". The card is designed to augment the effects of "Vampire Lord", "Vampire Lady", and the new monster "Vampire Grace", but it also works with other effects that mill your opponent such as "Gravekeeper's Servant" and "Iron Chain Dragon". The Trap Card, "Vampire Takeover", is very handy for getting "Kingdom" onto the field, and as well as a free Special Summon from your Graveyard. The main idea behind this strategy is to eliminate key cards in your opponent's Deck and controlling their field.
With Shadow Specters support, "Vampires" make an effective Xyz Monster Deck. Using the effects of "Shadow Vampire" and "Vampire Duke" to Special Summon level 5 DARK "Vampires" (such as each other or "Vampire Lord") and Overlay for the boss of the Deck: "Crimson Knight Vampire Bram". You can also use "Vampire's Curse" and "Vampire Grace" for Rank 6 plays, as well as "Zombie Master" for Rank 4 plays with monsters such as "Vampire Lady" or "Vampire Sorcerer".
"Vampire Sorcerer" is very helpful for both of the Deck's goals. Its first effect allows you to search any DARK "Vampire" monster or any "Vampire" Spell/Trap Card, and its second effect allows you to Normal Summon one "Vampire" monster without Tributing. You can use its first effect to search for "Vampire Kingdom" and its second to Summon "Vampire Lord" or "Vampire Grace" in order to mill your opponent, or you could search for "Shadow Vampire" and use the second effect to Normal Summon it, use the effect "Shadow" to Special Summon "Vampire Lord", and Overlay for a DARK Rank 5.