If I get this correctly, it's a creature card with 'Eclipse' as a passive ability (basically, Eclipse on a stick) for Light based-creatures, in which case it's also correspondingly buffed by it's own passive ability?
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AND it's immortal?I would say that this would be overpowered, but the fact that the Eclipse effect only lasts a certain amount of turns is a good start to not make it such a strong card. If the '4 turns' also applies to its immortality effect, then that helps as well, but to me, the damage it deals (as well as its cost) seem a little off. How about you reduce the damage of both cards by say, 1 or 2, and lower the cost correspondingly?
However, if it's going to be immaterial when it comes right into play, then I feel that
would like to have a one-on-one with you in private.