Corrupted Dryad

Spellcasting. The druid is a 4th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 12, +4 to hit with spell attacks). It has the following druid spells prepared:

Cantrips (at will): druidcraft, produce flame, shillelagh

1st level (4 slots): entangle, longstrider, chaos bolt, thunderwave

2nd level (3 slots): spike growth, acid arrow

Regeneration. At the end of every round of combat, the dryad regains 1d4+2 hit points as long as it is standing on some form of vegetation. The vegetation is blighted and dies afterwards. 

Quarterstaff. Melee Weapon Attack: +2 to hit (+4 to hit with shillelagh), reach 5 ft., one target. Hit: 3 (1d6) bludgeoning damage, 4 (1d8) bludgeoning damage if wielded with two hands, or 6 (1d8 + 2) bludgeoning damage with shillelagh.