This is basically Efreet... but without the lava!

Tephra is the volcanic ash and rock fragments produced by an eruption. So this is a decor that would make your lion look ashen and or as if it's vessel is crumbling apart. Another way to imagine it would be Hollow, but for the whole lion.

The decor would probably have to be behind a storyline wall, like Efreet and Hollow, to make it fair for those who earn Efreet or Hollow.

P.s. There might already be a decor like this, but I'm a bit ignorant on decors so I wouldn't know. Sorry if so!