Note for beams: if a dormant minion is placed in the immediate path of a portal beam, it will visually interrupt the beam and instead of carrying on to the next non-dormant minion, actually will buff Netherspite as if there were no minions in the path. This big goes away once the dormant minion awakens.
"The very top level of Karazhan is Medivh's private quarters. This is where Medivh opens portals to far off lands. And the creature that helps control those portals is the fearsome dragon Netherspite."[1]
Netherspite assists Medivh in the opening and controlling of various portals, to locations both across Azeroth and far beyond. Netherspite Historian appears to be researching the great nether dragon.
"Oh, splendid! Netherspite is away preparing the arrival portals for tonight’s guests. Netherspite is Medivh’s laboratory assistant and portal master. He also happens to be a dragon, and very serious about his experiments. In addition to his considerable knowledge of all things arcane, Medivh is something of a master of portal arcanology. I’m assuming that arcanology is a word. Regardless, from this very chamber, you can access realms and regions beyond imagination! The possibilities are endless, but we really shouldn’t touch anything." - Moroes[2]
In World of Warcraft
Netherspite's appearance in the Karazhan raid is a distinctive fight involving three coloured beams, which the players must block to prevent the dragon from gaining their benefits. This is recreated in Hearthstone, with minions used to block the dragon's two beams.
Netherspite is an immense nether dragon found lurking in the Celestial Watch, Medivh's personal observatory. As the only dragon found inside the dark tower, he will use his otherworldly powers to vanquish any creatures that attempt to go near him. This dragon's death is not required for further progress into the tower but he does control the trash between the Shade of Aran and the Chess Event.
There are two phases to this fight that Netherspite alternates between. The Portal phase, (the first one) lasts for one minute, and the Banish phase (the second one), lasts for half a minute. He alternates between these two at the given rate until dead or enraged.
Portal phase
Netherspite in World of Warcraft
Players get a system warning: "Netherspite cries out in withdrawal, opening gates to the nether."
At the beginning of this phase, three portals of different colors will spawn at fixed locations in the room and will begin emitting a beam of their respective color (see below) towards Netherspite. The beams do not slowly move toward him, but rather appear touching Netherspite once they are created.
If the beams are allowed to hit Netherspite freely, they grant him stacking buffs which strengthen or even heal him. The buffs on Netherspite last 5 seconds from last application (instead of the 8 to 20 seconds they do on players). The beams can (and must) be blocked by players who position themselves between a portal and Netherspite. Players blocking the beams are also affected by a stacking buff, having both a positive and a negative effect which grows more extreme with each second that the player spends blocking a beam. Although the positive effects are quite helpful for the fight, the negative effect makes it difficult (but certainly not impossible) for one player to block a beam for the complete duration of the Portal phase.
Once a buff "ticks out" (player leaves the beam long enough to lose the debuff — 8-20 sec), another debuff is applied to the player called Nether Exhaustion, which prevents him from intercepting that color beam for the next 1 minute and 30 seconds.
This part of the fight relies on individual player responsibility in that all players designated to block a beam ahead of time (see below for suggestions) must be aware of what beam they are supposed to be blocking and when so as to intercept it as quickly as possible.
Those not blocking a red beam deal damage or heal the raid. Because of the red beam's unique abilities, healers should not ever waste time healing the tank. Damage dealers need not worry about threat, since the tank has guaranteed aggro while standing in the red beam.
The portals shown in Netherspite's art lead to the Firelands, Silvermoon City, Moonglade, the Maelstrom and what appears to be Netherspace or the Twisting Nether. Likely intended to depict the adventure's five Portal spells, the warlock-themed portal may depict a removed spell, replaced by the warrior's Ironforge Portal, which does not feature in the art.
While special quotes by bosses in response to card played had become quite common by the time of One Night in Karazhan, the Raid Leader's custom quotes for this encounter are the first time a minion has had its quotes changed to match a boss encounter.
This section uses content from the Warcraft Wiki.
Moonfire
Mulch
Unstable Portal
Netherspite Historian appears to be researching the great nether dragon.
This section uses content from the Warcraft Wiki.
Patch 6.0.0.13921 (2016-08-09):