Bubamara

Lightning Absorption. When Bubamara is subject to take lightning damage, Bubamara regains hit points equal to the lightning damage dealt.

Gnome Cunning. Bubamara has advantage on Wisdom, Intelligence, and Charisma saving throws. 

Spellcasting. The artificer is a 20th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). The Bubamara has the  following Artificer spells prepared:
Cantrips (at will): Shocking grasp, Spare the dying, Mage hand, thunderclap, ray of frost
1st level (4 slots): witch bolt, false life, identify, grease, detect magic, cure wounds.                                                     
2nd level (3 slots): aid, alter self, dragon’s breath, invisibility, enlarge/reduce, web.                                                  
3rd level (3 slots): lightning bolt, animate dead, dispel magic, blink.                                                                                 
4th level (3 slots): Blight, Death ward, stone shape, summon construct, fabricate.                                                     
5th level (2 slots): Antilife shell, Bigby’s hand, Wall of stone, Animate objects. 

Multi-attack. You can make 2 attacks, consisting of Lightning Slam or Soul Sucking Snipe in any order.

Lightning Slam Melee Weapon Attack: +12 to hit, reach 10 ft., 1 target. Hit: 31 (5d10 + 6) Lightning damage.

Soul Sucking Snipe. Ranged Spell Attack: +12 to hit, range 300 ft., 1 target. Hit: 31 (5d10 + 6) Necrotic damage.

Lightning Revolt. (Recharge 5-6) When BubaMara is attacked by a creature within 5 feet of Bubamara, Bubamara can deal 6 (1d12) lightning damage to the attacker.

After a creatures turn takes place, Bubamara can take a legendary action. Bubamara can use 3 legendary actions per his turn. 

Lightning strikes (Costs 1 Action). Bubamara uses Lightning slam.

Thunderous shield (Costs 1 Action). Bubamara gains a +3 bonus to AC and No one can have advantage on attacking him. Together the effects last until his next turn. He can’t do this 2 rounds in a row, and the effects last until doesn’t stack.