interesting card. Seems very strong at first glance but the delay'edness of the three devourer might just be enough to counter it.
personally I think the base creature stats (6/5 and 7/5) seem a little high for 7
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. its certainly slower then vampire and gargoyle but you have the potential for 3 more cards. its a tough call it could be good but maybe to much.
It would be nice if it didnt steal gargoyles place at unupped or upped but was meaty'er then minor vampire. So maybe a 4/4 or 4/5 at unupped. and maybe 6/5 at upped.
just my take on it