Overly complicated kill

[Leviathan]

 {Eternal Witness}/ {Archaeomancer}
{Ghostly Flicker}
{Sphinx-Bone Wand}
{Gilded Lotus}

Use lotus to add 3 {U} mana to pool, use  {Ghostly Flicker} to flicker  {Eternal Witness} or  {Archaeomancer} and  {Gilded Lotus}. Use witness/Mancer to bring back  {Ghostly Flicker}. Repeat while  {Sphinx-Bone Wand} collects counters and shoots your opponent.

Add  {Inexorable Tide} to speed things up. =D

[Umbra]

Kind of mana costly, I would say  {Gilder Bairn}, {Training Grounds},  {Paradise Mantle},  {Shrine of Burning Rage}. All you need is 4mana max