Need an ecl for a players "race"

[Fiendish_Dire_Moose]

To do this with feats would require a spell like ability of greater teleport, then taking the quicken spell like ability feat for greater teleport. This is impossible pre epic. And even then, its only once per round.

So a level 22 character could do a quickened greater teleport as an SLA only 3 times per day, and your player wants this at will, more than once per round?

LA +10.

This. Teleport is powerful. Teleport at will is over powered. Perfect teleportation at will as a free action is literally epic+. I can't think of a monster that has it. Unless your game is 30+, don't give them it. and with Tomb of Horrors, they'll teleport past all traps. DON'T GIVE IT TO THEM.