Dragon Rider

Dragon Rider costs {2}{r} less to cast as long as you control a Dragon.
While you do not control a Dragon, Dragon Rider can't attack or block.
While you control a Dragon, Dragon Rider becomes a copy of target Dragon you control, except it's a 2/2 red and black Human Soldier Wizard.
If a Dragon you control is destroyed, sacrificed or exiled while you control Dragon Rider, sacrifice it if you control no more Dragons.