Crystalline dragons subsist on a diet of ore and gems. They are also particularly fond of the crystallized remnants of adventurers’ equipment, considering them a special taste treat. Glaciers are an ideal home, because as they slowly crawl across continents they scrape up tons of rock and soil. The crystalline dragon uses its massive, sharp claws to burrow through the hard-packed ice in search of veins of mineral-rich strata scraped centuries before from the earth’s skin.
Looks like an evil counterpart of the couatl, or an evil amphiptere. We can look to other serpentine dragons like the Styx dragon for constrict damage progression if we're not going to keep the values in the table. Seems like Small to Gargantuan.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.