Lidless Wall is a Unique Shield in Diablo IV Season 15. It drops from Andariel (Echo of Andariel).
Unique power
Lucky Hit: While you have an active Bone Storm, hitting an enemy has up to a [35 - 45]% chance to spawn a Bone Storm around their location. Each Sacrifice bonus increases this chance by 25% and allows you to spawn 1 additional Bone Storm. Each active Bone Storm grants 30% Critical Strike Damage, up to 150%.
Affixes
20.0% Block Chance
+100% Main Hand Weapon Damage
+0.5-8.5% Critical Strike Chance
Where it drops
Andariel, Maiden of Anguish (Lair Boss) per one guide
Random world drop / any Lair Boss (one guide: 'drops at any Difficulty Tier, increased drop rate per Torment tier'); 3.2.1: all Uniques drop from level 1 in any Difficulty; targetable via Horadric Cube reroll