xtherion: command not found

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

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

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/xtherion - from package: therion

You may install the required package with command apt-get install {package}

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