Frostbite

Overview

Virus (pl. Virii) is a cheap death creature that can be sacrificed to infect any creature on the field. When upgraded, it becomes Retrovirus (pl. Retrovirii), which for a slightly higher cost plagues the opponent’s field, poisoning all of his/her creatures instead of just one.

Oracle Fortune

Today, the old must give way to the new.
Someone near you will sacrifice themselves to bring your challenges down to size.

General Use

Quick Facts:

• Virus and Retrovirus are, somewhat humorously, not poisonous. They are, however, airborne.
• Retrovirus is among a handful of cards that change significantly from their unupgraded form.
• Virus and Retrovirus are the only creatures in the game that can sacrifice themselves.

For this article, unless otherwise noted, ‘Virus’ refers to both Virus and Retrovirus.

Virus, being a card that sacrifices itself in order to poison other creatures, ultimately causing multiple deaths is most often used in decks revolving a cards that use death effects, such as Bone Wall, Boneyard, and Soul Catcher. There are several ways to enhance the relatively small power of a single Virus, such as using Fractal or Mitosis to make several Virii, which are then sacrificed in large quantities, Retrovirus is especially effective with Fractal.

Another way to get more death effects is by using Sparks alongside Virii, either alone or with Fractal, as Spark has 0 HP, meaning it dies after attacking and thus also generates death effects. It’s also worth noting that using creature control on it triggers a death effect one turn sooner, in exchange for preventing a second later, making creature control less effective against many Virus decks.

However, Virus has uses without death effects, as well. Unupgraded Virus, due to its cost of only one quanta, can be used along with Immolation, which sacrifices a creature in order to build up quanta and one quanta in every other element. While this seems redundant, in many cases with Immolation, you have additional fodder – i.e. cards for the sole purpose of targeting with Immolation. While most fodder is useless without Immolation, Virii aren’t, as they can be sacrificed for their creature control.

Additionally, Virus has a number of quirky interactions with other cards. It is airborne, meaning it can hit through Wings, which could be significant in boosting damage with Fractal, and Iridium Warden, when buffed, cannot kill it to prevent the poison from happen. It’s also affected by Shard of Freedom, although its single attack and use for sacrifice makes use of this interaction difficult. Its poison can also open up uses with creature control cards that depend on lowering HP, such as Otyugh, Scarab, and Maxwell's Demon.

One final note is that Virus sometimes has bugs with Aflatoxin, as shown here and here

Synergies

Fractal allows you to target a creature and fill your hand with up, up to 8 copies. With Virus, this means several death effects the next turn, with a high chance that you can kill multiple threats of the opponent quickly. With Retrovirus, although it’s more expensive, this effect is even more pronounced, as the instant death effects with sacrificing the Retrovirii are accompanied by piling massive amounts of poison damage on the opponent’s creatures. This means death effects build up extremely quickly.

Speaking of death effects, Soul Catcher generates unupgraded ( upgraded) every time a creature dies. This, especially in conjunction with Fractal, but even without, can lead to a high amount of quanta generation, which can then be used for Bone Dragons, a Bone Wall which is then powered up by even more deaths, or Flesh Recluses when upgraded. Dragons and recluses can then be targeted with Fractal, and with enough quanta will easily swarm the opponent to death

Another powerful synergy is Otyugh. Otyugh has the capability to devour creatures with less HP and gains attack and HP with every kill. Virii or Retrovirii can whittle down HP of enemy creatures, allowing Otyugh to eat them more easily. Furthermore, since Virus is counter-intuitively not poisonous, Otyugh will not be poisoned by eating them, which means in a pinch, it can safely eat them for a bit of additional strength.

Other Cards With Synergy

• Mitosis can be used similarly to Fractal. It’s cheaper, but it’s not as effective, as you have to have a Virus survive in order to work, and Life generally has less synergy to work with.
• Bone Wall and Boneyard, much like Soul Catcher, feed off of death effects. Bone Wall gives you a powerful defense and Boneyard can give you a field full of Skeletonss, which a well-balanced Darkness duo can charge up with Eclipse for a powerful army.
• Scarab and Maxwell's Demon can be used similarly to Otyugh. Scarabs also have Devour, while Maxwell’s Demon can kill creatures with more attack than HP.
• Immolation can be used with Virus, as the latter is only one cost, and any extra Virii can be used for their ability to poison creatures.

Conclusion

To summarize, Virus is a card that appears weak, but has an interesting ability that synergizes well with several card, and can potentially be used in some very potent strategies if wielded correctly.

Popular Deck

Rotten Flesh

52h 52h 52h 52h 52h 52h 52i 52i 52i 52i 52i 52i 52p 52p 52r 52r 52r 52r 52v 52v 52v 52v 52v 52v 61p 61p 61p 61p 61p 61p 8pk

Other Decks

Note: Many of these decks may not be optimized. Use at your own risk.

Unupgraded

Wall of Disease
Graveyard Pickin’s
Death Scarabs
Shining Corpses
Immocats – Switch out the Cats for Virii and see how it works!

Upgraded

Supervirus
Soultal
Black Death
Contaminated Waters
Virus SouFflétal – Some would say your brain has to be Frozen to try this.