Too card specific... (those who're still playing Duel Masters will know what I mean )
^^^
Problems:
1) Death mechanic and theme but the element is not Death?
2) Time element but the mechanic is does not fit Time?
3) Enchanting Graveyards outside of Earth could be justified but not in Time.
4) A card tax/ forced combo is clumsy design. EtG is about versatility and options. Each card is meant to expand the metagame and thus enrich and diversify the gameplay experience.
Card Design Tips:
1) Versatility contributes to an increased metagame
2) Simple is good
3) Subtle design is elegant design
How about "Target Death Permanent gains : Generate a Skeleton"? Currently only applied to Boneyard and Soul Catcher. Making non- permanent to have the skill just doesn't fit thematically, imo.
This is better because it lets the skull be used with any of 7(8 if marks count) cards. However Death is still upset you are suggesting putting one of its cards in time rather than Death.