therion: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/therion - from package: therion

You may install the required package with command apt-get install {package}
Error in other languages:
therion: bevel nie gevind nie
therion: comandă negăsită
therion: comando não encontrado
therion: commande introuvable
therion: command not found
therion: käsku ei ole
therion: không tìm thấy lệnh
therion: komanda nerasta
therion: Kommando nicht gefunden.
therion: kommandot finns inte
therion: komut yok
therion: nie znaleziono polecenia
therion: níor aimsíodh an t-ordú
therion: no se encontró la orden
therion: no s'ha trobat l'ordre
therion: opdracht niet gevonden
therion: parancs nem található
therion: perintah tidak ditemukan
therion: príkaz nenájdený
therion: příkaz nenalezen
therion: команда не найдена
therion: командата не е открита
therion: 命令找不到
therion: コマンドが見つかりません