Greater basilisks are often used for guardians of treasure. Its own gaze, however, is effective to 50’ - no range is listed on the MM1 for the basilisk.
If not then there’s only a 10% chance it’ll see its own gaze.
Presumably since these beasts are sometimes encountered in pairs they’re immune to this effect. poison (at +2) or die each round they’re exposed. This means it gets two claws and a bite attack for d6/d6/2d8 damage instead of a single d10 bite. Still, here’s how the greater basilisk outshines its smaller brethren: I’m not sure how I feel about the creature itself, because gaze attack creatures don’t seem to me like they need powering up in general.