Boss Encounter 14 - lvl 5 to 10

Electrobear Large beast , unaligned
Armor Class 15 (Natural Armor/Plate) Hit Points (6d12 + 140) Speed 40 ft., climb 30 ft.
STR 22 (+6) DEX 10 (+0) CON 20 (+5) INT 15 (+2) WIS 12 (+1) CHA 7 (-2)
Saving Throws STR +10, CON +9 Skills Perception +3 Damage Vulnerabilities Acid, Piercing Damage Resistances Cold, Slashing Damage Immunities Poison Condition Immunities Frightened, Poisoned Senses Passive Perception 18 Languages -- Challenge 12 (8,400 XP) Proficiency Bonus +4
Keen Smell. The bear has advantage on Wisdom (Perception) checks that rely on smell.
Actions Multiattack. The bear makes two attacks: one with its bite and one with its claws.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 16 (2d8 + 8) piercing damage. If the bite Attack hits, theres a 10% change that the target is grappelled for 1 round. After that round, the effect bluetooth is added. If the target is grappelled the multiattack is nullefied.
Electroshock Bite. Control effect: The target is stunned for the next turn.
Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage, 5 (1d4 + 3) lightning damage.