Medium monstrosity, chaotic neutral
Armor Class 12 in humanoid form, 14 (natural armor) in monstrous spider and hybrid form
Hit Points 45 (7d8 + 14)
Speed 40 ft., climb 20 ft.
STR 11 (+0) DEX 15 (+2) CON 14 (+2) INT 14 (+2) WIS 13 (+1) CHA 14 (+2)
Skills Perception +5
Senses darkvision 60 ft., passive Perception 15
Challenge 2 (450 XP)
Innate Spellcasting. The aranea’s spellcasting ability is Intelligence (spell save DC 12; +4 to hit with spell attacks). The aranea can innately cast the following spells, requiring no material components.
At will: dancing lights, light, minor illusion
3/day each: charm person, invisibility, mirror image, silent image, sleep
Shapechanger. The aranea can use its action to polymorph into a Medium spider-humanoid or into a humanoid, or back into its true form, which is that of a monstrous spider. Its statistics, other than its AC, are the same in each form. Any equipment it is wearing or carrying isn’t transformed. It reverts to its true form if it dies.
Spider Climb. The aranea can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Web Walker. The aranea ignores movement restrictions caused by webbing.
Multiattack. In humanoid or hybrid form, the aranea makes two shortsword attacks.
Bite (Spider or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) piercing damage plus 7 (2d6) poison damage. At the end of each of its turns, the target must make a DC 12 Constitution saving throw, taking 7 (2d6) poison damage on a failure or ending the recurring poison damage on a success. A lesser restoration spell cast on the target also ends the recurring poison damage.
Shortsword (Humanoid or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) piercing damage.
Web (Recharge 5–6) (Spider or Hybrid Form Only). Ranged Weapon Attack: +4 to hit, range 30/60 ft., one creature. Hit: The target is restrained by the webbing. As an action, the restrained target can make a DC 12 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 10; hp 5; vulnerability to fire damage; immunity to bludgeoning, poison, and psychic damage).