Gearmass

Amorphous. Move through space 1ft.+ wide with o squeezing.

Clanging Mass. Is filled with metal objects that clang scrape and clink together as it moves. When it moves it has disadvantage on Dex (Stealth) checks to stay silent until start of its next turn.

Ooze Nature. Doesn't require sleep.

Rust Metal. Any nonmagic metal weapon that hits gearmass corrodes. After dealing damage weapon: permanent cumulative -1 penalty to damage. If penalty drops to -5 destroyed. Nonmagic metal ammo that hits gearmass destroyed after dealing damage.

Multiattack. Two Gear Slam or Cog Tossess. If it hits one creature with both Gear Slams target is grappled (escape DC 14) and gearmass uses Engulf on target.

Gear Slam. Melee Weapon Attack: +6 to hit, 10 ft., one creature,. 12 (2d8+3) bludgeoning damage.

Cog Toss. Ranged Weapon Attack: +6 to hit 20/60' one creature. 12 (2d8+3) bludgeoning damage and the target must make DC 14 Str save or be knocked prone.

Engulf. Engulfs Med or smaller creature grappled by it. Engulfed target is blinded restrained and unable to breathe and it must make DC 14 Con save at start of each of gearmass's turns or take 14 (4d6) acid. Any nonmagical ferrous metal armor weapons or other items target is wearing corrode at start of each of gearmass's turns. If object is either metal armor or metal shield being worn/carried it takes permanent and cumulative -1 penalty to AC it offers. Armor reduced to AC of 10 or shield that drops to a +0 bonus is destroyed. If object is a metal weapon it rusts as described in the Rust Metal trait. If gearmass moves engulfed target moves with it. Gearmass can have only one creature engulfed at a time.