The chelicerae has advantage on saving throws against spells and other magical effects.

The chelicerae cannot replenish its spells naturally. Instead, it uses grappled spellcasters as spell reservoirs, draining uncast spells to power its own casting. Whenever the chelicerae wishes to cast a spell, it consumes a number of spell slots from its victim equal to the spell slots necessary to cast the spell. If the victim has too few spell slots available, the chelicerae cannot cast that spell. The chelicerae can also draw power from drained spellcasters or creatures without magic ability. It can reduce a grappled creature’s Wisdom by 1d4, adding 2 spell slots to its spell reservoir for every point lowered. A creature reduced to 0 Wisdom is unconscious until it regains at least one point, and can’t offer any more power. A creature regains all lost Wisdom when it finishes a long rest.

Chelicerae can climb difficult surfaces, including upside down on ceilings, without requiring an ability check.