Gritshell

A Found Swamps mob stays hidden asleep beneath the mud until a player ventures too close, then it awakens and attacks. The mini-boss gives players a new challenge and adds some variety to the world, appearing in swamp areas instead of only in fixed structures. The Morgenstern is a morningstar weapon that interacts with shields. Hitting a shield with it needs the Scaring enchantment, and the cooldown after a hit depends on the enchantment level. The weapon is slow, so a player who raises a shield before striking gains a damage increase, and it partially ignores armor.

The Morgenstern core is crafted from a few iron nuggets and a chain stick, while the Shell armor piece is crafted from six shell shards and one iron ingot. The Shell has only 100 durability, and a player cannot see anything from inside it. Healing received while wearing it is less effective without it. Gritshell runs on client and server, so the server and every player need it. Files are published for Forge 1.20.1 only, with 1.3 as the latest release, under the Apache License 2.0. The license is permissive, but the mod is not open source.