o_0 Hello, BbtD. Goodbye, opponent.
Yeah, thanks to the oh-so-convenient 20-counter kill. =P Seriously, even with barrel exploit that's how many it would take to deal, and at that point I think I'd sooner go for the kill with Cloudbreak Dragon.
Striker Master: I do believe that this one is meant to be played together with Miscount, eh? Ah well, a 10-card difference isn't that easy to build either. Yay for super special awesome situational win conditions. x3
Moon Phase: Fine now.
Choose Your Prize!: Lawl, I have this mental picture of the dude from the Reversal Quiz and Quesion! illustrations choosing between doors A and B now. xD *Shot* Anyway, this is blatantly abused by Dark World since they turn it into a win/win and it's generally a case of big profit versus relatively small loss. Try making the loss a bit more painful. :3
Aaanyhow, back to the good old parasites. For those who weren't around back then, the originals can be found on page 19 of this thread. I've done some wording revisions and altered a lot of the effects. Lookie:
Cleansing Seal
Field Spell
All "Parasite Demon" monsters on the Field have their Atk and Def reduced by half and may not attack or change their Battle Positions.
Demonic Summoning Flute
Quick-Play Spell
Select one "Parasite Demon" monster from your Hand and Special Summon it to your opponent's Field, ignoring summoning conditions. Then, pay a number of life points equal to 800 x the number of tribute(s) mentioned in the card's effect. On the turn this card is activated you may not summon any other monsters (Including Flip Summon).
Blood Pact
Normal Spell
Select one "Parasite Demon" monster from your Graveyard then pay a number of life points equal to 200 x the level stars of the target monster and Special Summon it to your Field, ignoring summoning conditions.
Excorcism
Normal Spell
Select one "Parasite Demon" monster on the Field and destroy it. The controller of the card destroyed by this effect loses Life Points equal to half the original Atk of the destroyed monster.
Poltergeist
Normal Spell
Destroy one "Parasite Demon" monster on your opponent's Field to look at your opponent's Hand, then select one card from your opponent's Hand and discard it.
Violent Purge
Normal Trap
Destroy all face-up 'Parasite Demon' monsters on the Field. For each monster destroyed by this effect, inflict 800 damage to the controller of the card(s).
Demon Symbiosis
Continuous Trap
During each of your Standby Phases, if this card is face-up on your Field, pay 500 Life Points, otherwise this card is destroyed. While this card is face-up on your field, you may discard one "Parasite Demon" monster from your deck in order to negate an attack from one of your opponent's monsters.
Parasite Demon Karasu
Fiend/Effect
3 Star/Dark
1550 Atk / 600 Def
This card can be Special Summoned from your Hand to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. Each time a card controlled by the controller of this card is sent to the graveyard, the controller of this card pays 200 life points. (This is not optional)
Parasite Demon Searinox
Fiend/Effect
4 Star/Fire
1800 Atk / 500 Def
This card can be Special Summoned from your Hand to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. During each Standby Phase, the controller of this card pays 300 life points for every monster card on his/her field. (This is not optional)
Parasite Demon Zeptiemus
Fiend/Effect
4 Star/Water
1600 Atk/1800 Def
This card can be Special Summoned from your Hand to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. Whenever the controller of this card would gain Life Points, the controller of this card loses that many Life Points instead.
Parasite Demon Nefreeti
Fiend/Effect
4 Star/Fire
2000 Atk / 1300 Def
This card can be Special Summoned from your Hand to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. Discard this card from your hand in order to add 'Cleansing Seal' from your deck to your hand. If there is no face-up Field Spell on the controller's Field, the controller of this card tributes one card on his/her Field during each of his/her Standby Phases. (This is not optional) If there are no cards to tribute, the controller of this card pays 800 Life Points instead.
Parasite Demon Saadat
Fiend/Effect
6 Star/Earth
2450 Atk / 1850 Def
This card can only be Special Summoned by Tributing 1 monster on your opponent's Field and is Special Summoned to your opponent's Field. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. During each of the controller's Standby Phases, if the controller of this card has more than three cards in his/her Hand, the controller of this card discards cards from his/her Hand until he/she has three cards in his/her Hand. (This is treated as an activation cost)
Parasite Demon Nishruu
Fiend/Effect
6 Star/Dark
2500 Atk / 1200 Def
This card can only be Special Summoned by Tributing 1 monster on your opponent's Field and is Special Summoned to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. While this card is face-up on the Field, the controller of this card must pay 600 Life Points to activate a Spell Card.
Parasite Demon Sherincal
Fiend/Effect
6 Star/Fire
2400 Atk / 1400 Def
This card can only be Special Summoned by Tributing 1 monster on your opponent's Field and is Special Summoned to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. While this card is face-up on the Field, the controller of this card must pay 600 Life Points to activate a Trap Card.
Parasite Demon Severash
Fiend/Effect
8 Star/Dark
2900 Atk / 2300 Def
This card can only be Special Summoned by Tributing 2 monsters on your opponent's Field and is Special Summoned to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monsters. The controller of this card must discard one card from his/her Hand in order to set a card from his/her Hand.
Parasite Demon Shamishra
Fiend/Effect
6 Star/Fire
2300 Atk / 600 Def
This card can only be Special Summoned by Tributing 1 monster on your opponent's Field and is Special Summoned to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. Each time the controller of this card discards a card(s) from his/her Deck (Other than by the effect of "Parasite Demon Shamishra"), he/she discards twice as many cards.
Parasite Demon Ihtafeer
Fiend/Effect
7 Star/Earth
2700 Atk/2200
This card can only be Special Summoned by Tributing 2 monsters on your opponent's Field and is Special Summoned to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. The controller of this card may only activate one Spell or Trap card each turn.
Parasite Demon Tsukuya
Fiend/Effect
7 Star/Water
2600 Atk / 2600 Def
This card can only be Special Summoned by Tributing 2 monsters on your opponent's Field and is Special Summoned to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. During each of the controller's Standby Phases, Special Summon one Parasitic Token (Fiend, 2 star, water, 550 Atk/650 Def) to the controller's side of the field in attack position. If there are no empty creature zones on the controller's side of the field, ignore this effect. While this card is face-up on the field, destroy all tokens on the controller's field that aren't named "Parasitic Token".
Parasite Demon Karashah
Fiend/Effect
10 Star/Dark
3600 Atk/2800 Def
This card can only be Special Summoned by Tributing 3 monsters on your opponent's Field and is Special Summoned to your opponent's Field. If you Special Summon this monster, you cannot Normal Summon or Set a monster during the same turn. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. During each of the controller's Standby Phases, the controller of this card tributes 2 cards from his/her field. If there are no cards to tribute, the controller of this card pays 1000 life points instead. (This is not optional)
Also, two brand new ones for good measure:
Parasite Demon Ferdeuce
Fiend/Gemini
4 Star/Dark
1700 Atk / 1200 Def
This card is treated as a Normal Monster while face-up on the field or in the Graveyard. While this card is face-up on the field, you can Normal Summon it to have it be treated as an Effect Monster with this effect:
-When this card is Normal Summoned successfully, control of this card is switched to your opponent. This card may not be offered as tribute except to Special Summon a "Parasite Demon" monster. During each of the controller's End Phases, the controller of this card must select and activate one of the following:
* Tribute one card on your Field.
* Discard one card from your Hand. (This is considered to be an activation cost)
Parasite Infestation
Continuous Trap
Discard one "Parasite Demon" monster from your Hand to activate this card. Select one face-up monster on your opponent's Field and equip it with this card. A monster equipped with this card can not be offered as tribute under any circumstances and is considered to have "Parasite Demon" in its name. During each of his her Standby Phases, the controller of the equipped monster pays Life Points equal to 100 x the level stars of the equipped monster.
Oh, and something that isn't a parasite:
Hands of Mischief
Normal Spell
This card can only be activated while there are three or more cards in your opponent's Hand. Select a card at random from your opponent's Hand and shuffle it into his/her Deck.