Legendary altars have a base 2% chance of spawning per biome, which increases by 15% for each biome that didn't spawn one, thus ensuring you find a Legendary altar in most of your runs. These altars hold a Legendary item and give the enemies nearby 33% damage reduction. The nearby enemies must be killed before you can grab the item, making it a high risk/reward situation.
Legendary items have powerful advantages:
- Colorless (scales with your highest stat)
- A specific affix (predetermined for each base item) with a 15% chance to be applied after all other affixes, ignoring the usual affix generation rules
- Cheap re-rolling cost
Legendary items are marked with a gold color, rather than the colors of the base item's scaling stats.
The item pool for Legendary items is not limited to unlocked items, but heavily skewed towards them. It is possible to get any item other than the Symmetrical Lance on a fresh save, but it will be much more likely to get an item from the starting pool. On saves with all items unlocked, the chances of getting any item seem to be equal.