Greavers are a type of monster found in the Clockworks.
Greavers resemble large bats crossed with moths, like their smaller cousins, the Wings. Unlike Wings, however, Greavers are not passive healers. They will follow a knight and swoop in when preparing to attack, hugging their target's behind closely for a few moments before hitting.
As adventurers progress down later tiers, Greavers will also gain the ability to shoot bullets and leave a status-inflicting haze after attacking.
Greavers move fairly quickly when preparing to strike, so a knight charging his own attack is unlikely to outrun them. They stick to their targets long enough before attacking for you to cancel your charge or move out of range. Push them away with your shield or dodge their hits before counterattacking. Try not to stay in one place or move towards the Greaver after shielding from its attack in later tiers, as the haze can affect you through your shield.
Greavers can be easily disrupted by most attacks, so you can avoid being hit by one or two Greavers by hitting them then retreating a short distance. One could even utilize Shield Cancelling to Shield Bump a Greaver back then prepare a Charge Attack. A group of them are particularly vulnerable to the wide swing of some Swords, like the Troika/Sealed Sword lines or any piercing sword such as the Flourish line. They could also be countered by any offensive Bomb like the Blast Bomb or Spine Cone lines.