Blue death feigning beetles, A. verrucosus, and they earn every word of that name.
Sonoran desert animals coated in a waxy blue secretion that helps them retain moisture, and when disturbed they flip onto their backs and hold a convincing dead pose for minutes. They live for years, sometimes many, which is remarkable for a beetle and a large part of the appeal.
Bone dry substrate. Genuinely dry. Keepers who add moisture out of instinct lose them to fungal issues, and this is the single most common failure. Almost all supply is wild-collected from Arizona and California, prices are very low, and availability is seasonal. Captive breeding is difficult and nobody does it at scale.