OUTSIDE
The most eye-catching characteristic on Riiva's appearance are definitely those two hooks penetrating hir throat and iron nails that go through hir wrists, the massive amout of scars on hir left front leg and right hind leg, pieces of leather that sutures hir mouth and that fact Riiva's heart is ripped out leaving only bleeding hole in the chest.
Also shi has slim piece of metal attached to hir back and making it hard for Riiva to even sit down. Five, very stict leather belts go around hir body on neck, sides and tummy.
Riiva has some sticking on corners of hir mouth - on left side those stickings are put on shape of XIV and on right side VIX.

Riiva's body is slender and shi has long legs, longish but very thin, white fur. Hir left ear is ripped away, right is floppy. Eyes are white and fairly big.

INSIDE
Riivahenki seems to lack hir own personality almost totally and basicly reflects what the others think of hir. Hence, Riiva can be almost anything - shi can be totally harmless or totally harmful and everything in between.

But in fact Riiva has personality. It's not very visible though, as shi seems to really enjoy just reflecting thoughts of others.
Anyway, shi is mischievous trickster and sees life as a one big game. Riiva seems not to be capable of feeling any strong, warm feelings for anyone and 'cause of that shi can't really be trusted.