It’s Griswalda and Elliot’s future mixed baby, Grishka! She is known as the “feral child“.

Grishka

• She's a Tundra Grimm and Diving Beetle hybrid. She's Griswalda and Elliot's youngest daughter. She's also Gridley, Grier, Grimmshaw, and Snowflake's younger sister.
• She's 3 years old and a girl.
• She's feisty, hyperactive, protective, noisy, and quite aggressive. Many would describe her as feral.
• Griswalda had her by accident, but she and Elliot love Grishka nonetheless.
• She was very aggressive towards non-grimms as a baby. It was so bad, Griswalda had to use a spell to mellow her out.
• They trained her to not attack others when she was 3 and it worked for the most part. If she feels wronged though, she will attack.
• The reason why she's aggro is because NKG put a bit of her great, great grandma's DNA in her. That ancestor was especially aggressive due to dealing with hunters and mortal bugs alike. This, of course, isn't particularly useful since the hunter threat is non-existent, so they use this aggressiveness in hunting instead.
• In teaching her hunting, this also resulted in Grishka going out by herself to hunt nearby fauna. It stresses her parents out but also mellows her out a bit so it's a double edged sword.
• Despite her feral nature, she loves her family a lot and is very upset when Gridley and Grier go off to college.
• She's closest to Snowflake, their adopted vessel and often translates for them