Wyvern Rider

Wyvern rider costs {u} less to cast if you
control any ally, goblin, knight, orc,
soldier &/or wizard.
Enchants any creature you control. That
creature cannot be an artifact.
Enchanted creature gets +1/+1 and gains
flying and wither. Enchanted creature also
gains the wyvern creature type.
Dragons have fire, wyverns have their poison
stinger. Wyverns are much easier to find as mounts.