Hmm, this is the third topic I've seen today suggesting a card which in one way or another, bypasses the immortality/protection feature.
Just out of interest, what did you vote for here? (
http://elementscommunity.org/forum/index.php/topic,2839.0.html)
Maybe Eclipse should do +1/+1 (+2/+1 upgraded) to Death/Darkness creatures and
maybe it should do -1/-0 (-2/-0 upgraded) to all creatures?
My thinking behind this is, to use it offensively, it would only really be useful if your opponent uses Life/Light - whereas, to use it defensively it is almost 100% certain that if you have an Eclipse in your deck, you will have mostly Death/Darkness creatures
.
Anyways, back to your idea.
If it does go through immortality on a permanent, then it is quite powerful, but in order for it to work - you would presumably have to carry a few 'non essential' weapons like Daggers or some Skull Shields as fodder for using this. Most streamlined decks I know only have 1 or 2 main weapons, and you would hate to give it to your opponent just for the sake of 'he has something better'.