Items, NPCs, quests, objects and spells of patch 1.12.1, read live from the realm itself.

Untested Basilisk Sample

NPC	Level	Zone	Chance
Glasshide Basilisk	42 - 43	Tanaris	100%
Glasshide Gazer	45 - 46	Tanaris	100%
Glasshide Petrifier	48 - 49	Tanaris	100%