The hyena is a beast known for its cruelty and madness. It is distinguished by the ridge of hair down its back, and its lion-like tail. The hyena is described in period heraldic tracts [Bossewell II.49], but no examples are known of its actual use in period heraldry. It doesn’t seem to have a default posture; the illustration shows a hyena statant.
Oriel Gibberish bears: Purpure, a hyena statant contourny argent semy of roundels purpure, a chief argent.
Andras le Lâche d’Armorique bears: Azure, a hyena salient to sinister ermine, charged on the shoulder with a heart sable.
Damian Mortmain bears: Per saltire azure and sable, a hyena passant argent marked sable maintaining in its mouth an arm proper, a bordure wavy argent.