Some interesting changes to pretty good OU mons:
Thundurus-Therian becomes Grass/Ground. Unfortunately still weak to Stealth Rock (Bug) and also has a pesky 4x weakness to ice, which means mach punch and vacuum wave maim it. Because Water becomes Fire, Aqua Jet also hurts it for a lot, especially from something like Azumarill. Offensively, however, Grass type Thunderbolt and Ice type Focus Blast are nothing to laugh at.
Terrakion becomes Bug/Ice. Becomes much worse defensively, getting maimed by any moves that change to fire and rock, such as Aqua Jet and Shadow Punch. However, it's good offensively, with Ice type Close Combat and Bug type Stone Edge.
Lucario becomes Ice/Dark. While this makes a crippling 4x Fighting weakness, the fact that Poison becomes Fighting and only a few Poison moves being viable makes Lucario relatively safe. However, a weakness to Stealth Bug does hurt Lucario's viability. Offensively, Dark type Bullet Punch is very good, as well as Ice type Close Combat and Fairy Extremespeed. On the special side, Lucario has Ghost type Dragon Pulse, Ice type Aura Sphere or Vacuum Wave, and Dragon type Dark Pulse to work with.
Kyurem-Black becomes Ghost/Electric. Cube is already an offensive behemoth in normal OU, and in shifters it's even stronger. Ghost type Outrage/Dragon Claw and Grass type Fusion Bolt hurt a lot. A resistance to Stealth Bug also helps Cube's Roost set be even more effective.
Thundurus-Therian becomes Grass/Ground. Unfortunately still weak to Stealth Rock (Bug) and also has a pesky 4x weakness to ice, which means mach punch and vacuum wave maim it. Because Water becomes Fire, Aqua Jet also hurts it for a lot, especially from something like Azumarill. Offensively, however, Grass type Thunderbolt and Ice type Focus Blast are nothing to laugh at.
Terrakion becomes Bug/Ice. Becomes much worse defensively, getting maimed by any moves that change to fire and rock, such as Aqua Jet and Shadow Punch. However, it's good offensively, with Ice type Close Combat and Bug type Stone Edge.
Lucario becomes Ice/Dark. While this makes a crippling 4x Fighting weakness, the fact that Poison becomes Fighting and only a few Poison moves being viable makes Lucario relatively safe. However, a weakness to Stealth Bug does hurt Lucario's viability. Offensively, Dark type Bullet Punch is very good, as well as Ice type Close Combat and Fairy Extremespeed. On the special side, Lucario has Ghost type Dragon Pulse, Ice type Aura Sphere or Vacuum Wave, and Dragon type Dark Pulse to work with.
Kyurem-Black becomes Ghost/Electric. Cube is already an offensive behemoth in normal OU, and in shifters it's even stronger. Ghost type Outrage/Dragon Claw and Grass type Fusion Bolt hurt a lot. A resistance to Stealth Bug also helps Cube's Roost set be even more effective.