Shield of the Order

Shield of the Order is an enchanted medium shield +4 which offers a -1 bonus to all saving throws. This item appears in Baldur's Gate II: Throne of Bhaal and Baldur's Gate II: Enhanced Edition and it's probably the best shield of the medium shields available. It's dropped by Yaga-Shura in the Siege Camp near Saradush.

In-game description
"Peragath the Valiant, a great champion of the Order of the Radiant Heart, carried this shield into battle against a horde of invading Tanar'ri pouring through a gate to the Astral Plane. Gripped by holy fervor, the mighty paladin single handedly drove back the horde, then foolishly leapt through the Astral gate to finish them off.  The gate collapsed, and both Peragath and the shield were forever lost in the Planes."