Dark Basalt (Basalt)

Basalt the Dark Battle Mammoth is a great dark tank support unit with lot of interesting CC features in Summoners War, his main utility is to help you get more turns as an AoE attack bar reducer with no glancing, while keeping bosses provoked and reducing the risk on your team during hard situations by applying a universal defense buff.

The dark mammoth is pretty good for Toa hard in all stages from 1 to 100 where he has to have 70% accuracy at least,  20k hp, 1500 def and more than 170 on speed.
Usually teamed up with Baretta, Verdehile (Fire Vampire), Mantura (Dark Serpent), Mav (Wind Penguin Knight) and Spectra (Fire Griffon).

He can also be used in Arena Offense with a slightly different build based on defense and critical damage, because his third skill multiplier is really high, but if you don't have two of them try keeping focus con accuracy and speed otherwise it will fail as a tool for toa hard.

Additionally his defense buff makes him a great alternative for Shannon (Wind Pixie) in giant B10.

Basalt Dark Battle Mammoth Suggested Runes

The rune type here will not make too much different unless you go for a despair set, otherwise choose a good mix for Violent, Guard and Focus depending
on what you have to achieve the required stats.

Damage Dealer (mainly Arena): Def%/CD/Def% - good mainly due to the Max Defense scaling of the third skill

Tank: Energy/Guard (Hp%/Def%/Hp%) - this will provide defense buff and a good threat for tanky light units like Darion (Light Vagabond) while taking the most out of his healing capabilities based on max hp.

Toa Hard king: Spd/Def/Def with substats focus on accuracy >80%, speed > 170 and at least 20k hp (even despair if you can fit with this stats)