The Mantid Egg Grenade is craftable post-moonlord throwing weapon. The thrown grenade explodes after a while or instantly when contacting an enemy, releasing a single 'micro mantid'. Inflicts Mantid Toxin. The 'micro mantid' chases after the enemy, bounces and pierces multiple times.
Even though the tooltip states that multiple mantids are unleashed, only a single mantid is released.