I always find it interesting how many old AD&D items, spells and monsters have such individual unique rules to them, that are similar but different from rules that another item, spell, monster, or class ability. One of the things I like about 5e and a modern rule set is the idea that you use a standardized rule.
Speaking to that, as design note, the girdle of lions has two abilities copied straight from class abilities. The monk's Slow Fall and the Rogue Thief archetype Supreme Sneak.
Girdle of Lions
Very rare wondrous item
This belt appears to be like any other magical girdle when first
encountered. When it is put on, you gain several special abilities. You can speak with felines (as per the spell speak with animals). The felines, from house cat to sabertooth tiger, will view you as if you had a Charisma of 18 (for purposes of reaction checks). Often the cats will give advice or assistance to you and may obey your command, if such are reasonable.
You also gain the ability to land on your feet from a fall. You can reduce any falling damage you take by an amount equal to five times your level.
The girdle also gives you the ability to move silently. You gain advantage on Dexterity (Stealth) checks if you move no more than half your speed on the same turn.
Finally, the girdle confers low light vision.