User blog comment:Reborn23/100% BB gauge reduction Krantz/@comment-30054866-20171224180924

Hullo! (owo)/

A 0 BC cost Krantz, huh. Well, it's definitely not impossible... but it'll be hard. Let me see what I can dig up.

Spheres

Projection Device: 20% BC requirement reduction, attained via Bound to Light

Defender's Blade: 20% BC requirement reduction, found in Colosseum Rewards (Stage 47, Red Chest)

Summoner Key: 20% BC requirement reduction, found by reaching HR 38 (Frontier Hunter) or by reaching "Ruling Star" in Arena

Harmony Vestments: 20% BC requirement reduction, found by reaching HR 74 (Frontier Hunter)

Four Bonds: 15% BC requirement reduction, found by completing "Four Heroes of Palmyna" Grand Quest (100% Reward)

Units (aside from the units you have already listed)

Atro: 25% BC requirement reduction

Kikuri: 20% BC requirement reduction

Solos: 20% BC requirement reduction

Gabriela: 25% BC requirement reduction

Quaid: 20% BC requirement reduction

Freed: 20% BC requirement reduction

Vern: 25% BC requirement reduction

I'll list some more down when I get the time. I hope this helped; and Merry Christmas! (^^)/