Channelers run around from floors 2-6 and are ussually posessed by Gastly or Haunter. The Cubone here act against their loner nature and travel in groups for some unknown reason.

The basement floors haven't been ventured in for about fity years. There are legends that mysterious Pokemon in the basement floors, though, none have been courageous enough to take a step down there to check.

Floors 1 & 7
No pokemon recored.

Floors 2-6
Gastly, Lvls 13-21, 1-70
Haunter, Lvls 15-29, 71-90
Cubone, Lvls 10-17, 91-100

Basement Floor 1
Unown A, Lvl 15, 1-10
Unown B, Lvl 15, 11-20
Unown C, Lvl 15, 21-30
Unown D, Lvl 15, 31-40
Unown E, Lvl 15, 41-50
Unown F, Lvl 15, 51-60
Unown G, Lvl 15, 61-70
Unown H, Lvl 15, 71-80
Unown I, Lvl 15, 81-90
Unown J, Lvl 15, 91-100

Basement Floor 2
Unown K, Lvl 25, 1-10
Unown L, Lvl 25, 11-20
Unown M, Lvl 25, 21-30
Unown N, Lvl 25, 31-40
Unown O, Lvl 25, 41-50
Unown P, Lvl 25, 51-60
Unown Q, Lvl 25, 61-70
Unown R, Lvl 25, 71-80
Unown S, Lvl 25, 81-90
Unown T, Lvl 25, 91-100

Basement Floor 3
Marowak, Lvls 29-37, 1-10
Sandslash, Lvls 22-30, 2-20
Zubat, lvls 15-21, 21-35
Geodude, Lvls 30-32, 36-40
Unown U, Lvl 35, 41-50
Unown V, Lvl 35, 51-60
Unown W, Lvl 35, 61-70
Unown X, Lvl 35, 71-80
Unown Y, Lvl 35, 81-90
Unown Z, Lvl 35, 91-100

There's a rickity old elevator On BF3 that leads many levels below.

Basment Floor 20
Only rocks tht may contain fossils are down here, here are the fossil types.

Helix Fossil: Omanyte
Dome Fossil: Kabuto
Old Amber: Aeordactyl
Skull Fossil: Cranidos
Armor Fossil: Sheildon

The fossils are very rare, though, supposedly, all of the stone that the Pokemon Tower is made of, contains Kabuto fossil pieces.
Old Ambers are very commonly found, but most believe it is just an ancient Mosquito stuck inside amber.