White Dragon is obtainable as a reward after defeating level 5 of the rare raid encounter.
Elafikeras is pretty much the best booster to any Earth unit for this raid. It has Pierce ATK+15, Earth ATK+25, and Lightning Eater+25, and all of those nodes can be picked up at 3-star max level. Its evocation ability also has a chance to inflict confusion, which Aigaion has no resistance to.
Oberon is the ideal choice of unit for this raid since Aigaion is weak to Earth and Pierce, but also because Oberon can lower Earth, Pierce, and All Elemental resistances even further. This allows your other party members to potentially reach the max damage per attack more easily. He can even solo it against level 100 Aigaion, but may be a little unreliable at times since there's always a chance of paralysis.
Frederika (Halloween) has Dragoon sub job for pierce ATK, but she doesn't handle Aigaion that well compared to Oberon when it comes to solo. She's still the second-best option to bring since she's in the "Large" bonus raid unit.
If you want to go with the Pierce attack route, Aileen and Glaciela are the more recommended options because of their raid bonus feature. Aileen has the elemental advantage but she's only in "Medium", while Glaciela is in "Large".
"Murmur" is a pretty good support damage dealer for this raid. With her EX upgrade, she's able to reduce enemy's DEF and SPR with one skill and reduce Earth resistance with another. There's also decrease ATK, MAG, and AGI down in 1 convenient ability. The cherry on top is that she also has Lancer sub job for some piercing attacks.
Clairvoyant Astrologer is a convenient support VC for spear wielding characters because it comes with a skill that can reduce DEF.
If you have Duane, then the usual mono Dark Slash comp will always work as usual. Since Duane can already reduce Dark and Slash resistance on his own, you can bring a unit like Vinera Fennes to reduce DEF and provide Confusion, or Shadowlynx for Single Target resistance down and multi-hit attacks.
Cloud may have a decent advantage compared to other Slash damage dealers, but only if you have Scorpion Sentinel esper. Cloud can reduce Slash resistance and get the 3 main benefits of Scorpion Sentinel for this raid since it has Slash ATK+, Lighting ATK+, and Machine Eater.
Starlight Elena can be a good addition to a Slash comp since she has plenty of multi-hit attacks, as well as having AGI+ and AGI- to slow down Aigaion for more chains. She can also inflict Confusion through her Kotodama sub-job if you need it. Unfortunately, she might need Illusory Bell to maintain consistent damage.
If you need some extra boost to damage via Eater nodes, then these are some of the options that you can bring.
Titan doesn't have a 3 star yet, but he's the next best thing for Earth Pierce damage dealers if you don't have Elafikeras.
Ochu is mainly for tanks since it mostly has defensive nodes.
Freizess has Machine Eater, but the nodes are mostly for Ice Magic damage dealers, which isn't recommended because of Aigaion's high magic resist.
White Marshmallow Miniature is a raid equipment from previous raids. It comes with some paralysis resistance, which is just to help reduce the chance of failing a fight.
White Dragon is also weak to Pierce, so you can pretty much use the same team to fight both raids.
Omega has both Light and Dragon eater to help any dark unit be a strong carry against White Dragon. Additionally, Omega has Slash ATK+ as well.
Two-Headed Dragon has Light ATK+, Slash ATK+, and Dragon Eater.
Diabolos has Light Eater, but stats and other nodes are for mages, which is less recommended since White Dragon has high MAG resist.
If you have no other good units, Lameiga and Demon Chimera are pretty decent budget options. Lameiga is in the "Medium" raid bonus that can use Strike attacks, and Demon Chimera has Dark ATK+, Light Eater, and some Evasion.