Mega Gigalith and a regional Ice/Grass Gigalith line!
Mega Gigalith, a pure Rock type, fortifies their rocky exterior to become near impenetrable! This fortress of a Pokemon releases deep sonic hums as it walks, attracting more of its kind. Should one mega evolve in the wild, the attracted pre evolutions will assist Mega Gigalith until the transformation ends. Special Defense and Defense raise dramatically, but Speed drops well into the low end of the stat ranges. Trainers wielding a Mega Gigalith should take great heed of hearing protection.
(Obligatory Evil and Sad Sun/Moon Entry: Mega Gigalith’s legs ache and strain to hold up their bloated body. Each step takes a monumental effort and the crystal casing on their head blocks out most senses, tanking the quality of life for this Pokemon. The power of mega evolution forces Mega Gigalith to emit a deep hum, causing them to rattle constantly.)
Alpine Gigalith, whose evolutionary line remains Grass/Ice, lives in high elevation taiga biomes. They compete with Abomasnow for territory, but are otherwise quite passive. Hikers and Rock Climbers recommend taking extra berries when passing through Alpine Gigalith territory as, while they will happily guide you to safety should you need it, they greatly appreciate the extra food.
by MeltedStones