Rune Guardians (DVM)

Function

This is a dungeon that you unlock when you are a member of a clan, and you have passed Nightmare Dungeon 10. This dungeon is very good for getting runes of a specific colour. Rune Guardian only gives out 5-star and 6-star runes.
There are 4 dungeons, each of which give out 2 sets of runes.

The Rune Guardian boss itself does not deal a lot of damage.
Instead, it mainly removes buffs from your dragons, as well as applying debuffs, and relies on its minions to deal out damage.
It is also bulky so to get through it quickly, your dragons will need buffs to increase their damage output.
Although the boss will be quick to remove buffs, it only removes 1 buff at a time, and you can stack multiple so that you always have some advantage over it.
Stacking debuffs can also be helpful, although the boss spawns minions, so it is as likely that the debuffs will hit minions than it hitting the boss.
Also, due to its high bulk, it is normal for runs to take a long time, usually 2-3 minutes per run or more. You definitely want to reduce this time as much as possible as you go along, but do not worry about it at first - as long as you can consistently beat the boss, you are doing well.

Even though this dungeon has the standard 2 waves of minions, Mini is not as good here as in other places. It is only really useful in the first wave, as the second wave has a bulky mini boss that Mini will not be able to deal with.
Instead, a good dragon for multiple-targets is Water or Dark Arkana. Their damage does not drop drastically when there is only one target, and they also buff themselves, something extremely useful in this dungeon.

Earth Hades is another good multi-target attacker, especially thanks to its DEF decrease, allowing your dragons to damage the boss more.

Fire and Dark Nerroth are support dragons, but their DOT support can be a great boon if you have them. Because the boss does not deal too much damage, it is perfectly viable to only have attackers in order to clear the minions, and use DOT to wear down the boss.
I highly recommend using 2 multi-target attackers, as the boss spawns minions, and your single-target attacker is more likely to target minions than the boss. However, the high damage output of a single-target attacker is still extremely useful, so do not fret if you have no good multi-target attackers to begin with.
Note: Wonder is not as effective in this dungeon as it is in other dungeons! The boss deletes buffs with its attacks, so it will get rid of Wonder the minute it turns into zombie.

You should only need 1 healer in Rune Guardian dungeons. Good healers for this are those that can boost your dragons’ ATK stat, such as Smart or Water Marshmallow. Light Lady’s ability to increase Critical Rate is also useful.

As always, you will need a mana battery such as Lamb or Cupid. Here, Lamb’s sleep or silence is useless, and its shield is not of much use either as it will probably be removed by the boss.
Earth and Water Cupid’s debuff, on the other hand, is much more useful, although on auto, it is likely it will end up on the minions rather than on the boss. This is where Dark and Fire are superior, as they provide buffs for your dragons.
You could also use a dragon that provides both mana and buffs, such as Light Pharaoh, equipped with Meditation runes. This clears up one team slot to add another support.

As you may have gathered by now, dragons that provide buffs shine in Rune Guardian. Without them, your run will be slow.
Light Pharaoh is always excellent to use for its 2x ATK buff (or Water if you use an ATK Speed party), as well as Nerroth, which is similar to Pharaoh with more utility.
Dark Party increases allies’ Critical Rate, which can be paired with Light Lady on a team of Critical DMG dragons.