Seems a bit too OP. We can compare it to Owl's Eye | Eagle's Eye, which is another form of repeatable CC.
Thwomp has:
a) 2
higher cost
b) same attack unupped but lower attack upped
c) higher hp
d) requires two elements
e) deals more damage per quanta upped
f) deals more
instant damage
g) an added insta-kill effect
h) can have multiple copies without the aid of another card
i) also flying
Points f, g, and h are probably the main reasons why this is too powerful.
