Edit: Renaming, buffing and nerfing
The Plaguebringer plans to annihilate all of Revnia with his plague.
The Plaguebringer brings a whole new unique mechanic to Spectromancer (or at least AFAIK). The Plaguebringer infects their enemy creatures via disease counters, then consumes them for additional devastating effects.
Design theme: Alien-like, insect-like, possibly a little like Zerg from StarCraft or aliens from the aliens movies
Plaguebringer special ability: Each time an enemy creature receives damage from the Plaguebringer's creatures or spells, that creature increases its disease counter by 1. *
*This includes non-disease spells such as chain lightning. Zero damage does not count, which means if an enemy giant turtle is attacked but it doesn't receive damage, its disease counter isn't increased.
Specialization: Disease
For strategy purposes, I'll be categorizing the cards according to their purpose: producers and consumers
producers primary purpose is to produce disease counters, while consumers either consume those disease counters for additional effect, or simply depend on the number of disease counters for their additional effect.
1. Infect - producer - Deal 6 damage to the target creature. This effect increases the target's disease counter by 2 instead of just 1. If the target dies due to Infect, the target's disease counters are spread to other enemy creatures randomly but evenly.
2. Locust Carrier - 3/24 producer - When Carrier is summoned and it is blocked, it immediately attacks all enemy creatures.
3. Infest - producer and consumer - The target enemy creature is stunned until the end of the opponent's next turn. If the target creature has only 2 disease counters or fewer, the target creature receives 12 damage and its disease counters turn to 3. If the target creature has 3 or more disease counters, Infest consumes all of the target's disease counters and deals 5 damage for all counters consumed by this effect.
4. Flying injector (originally named toxic wing) - 4/26 producer and consumer - At the beginning of each turn, Flying injector inflicts 1 damage to all enemy creatures. At the end of each turn, if an enemy creature has 4 or more disease counters, Flying injector consumes all of those counters and inflicts 4 damage to the creature for each counter consumed.
5. Soul Leech - 4/27 consumer - Each time an opponent's creature dies, Soul Leech inflicts damage to the opponent equal to the disease counters the creature had.
6. Desecrator (originally named Hive Queen) - 4/40 consumer - When Desecrator is summoned, it consumes all disease counters of all enemy creatures and inflicts damage to those creatures equal to the disease counters consumed x5.
7. Broodmother - 4/33 (originally 3/33) consumer - Each time an opponent's creature dies, Broodmother increases the owner's Disease power by 1 for every disease counter the creature had when it died.*
8. Titanclaw - 8/37 consumer - When Titanclaw is summoned, it destroys all enemy creatures with 3 disease counters or more.
Additional notes:
For the purposes of Soul Leech and Broodmother: when an enemy creature dies, it still gains an additional disease counter based on the attack or effect that caused its death. For example, if a priest of fire with 6 life had 3 disease counters, and you cast infect to kill it, infect's two additional counters are still added before the priest of fire's death. If you have a Soul Leech when this happens, Soul Leech deals 5 damage to the opponent(3 current disease counters plus infect's 2)
