Drow Arachnomancer

Medium humanoid (elf), chaotic evil
Armor Class 15 (studded leather)
Hit Points 162 (25d8 + 50)
Speed 30 ft., climb 30 ft.
STR
11 (+0)
DEX
17 (+3)
CON
14 (+2)
INT
19 (+4)
WIS
14 (+2)
CHA
16 (+3)
Saving Throws Con +7, Int +9, Cha +8
Skills Arcana +9, Nature +9, Perception +7, Stealth +8
Damage Resistances poison
Senses blindsight 10 ft., darkvision 120 ft., passive Perception 17
Languages Elvish, Undercommon, can speak with spiders
Challenge 13 (10000 XP)
Change Shape (Recharges after a Short or Long Rest).
Fey Ancestry.
Innate Spellcasting.
Spellcasting.
Spider Climb.
Sunlight Sensitivity.
Web Walker.
ACTIONS
Multiattack.
Poisonous Touch (Humanoid Form Only).
Bite (Giant Spider Form Only).
Web (Giant Spider Form Only; Recharge 5–6).

This full creature's stat block is not available (not OGL).

Mordenkainen´s Tome of Foes
Drow Arachnomancer