I say take the cards that the flying weapon rainbow deck could use. This way if we survive next round and loot some good cards, we can potentially make a deck like that.
We are fighting
and
. Fire will probably play fractal phoenix and entropy will probably play black hole deck. Even assuming we win both, we can hardly combine those looted cards with those we are looting now to form a new deck with synergy. Entropy loot may support our entropy darkness and fire deck support, well nothing. We can still make a flying weapon rainbow deck by converting to quantum pillars.
After this point, we can hardly build a new mono or duo deck so we can make a rainbow on next rounds. We had that chance last round when we had tons of air cards.
So my suggestion is like;
Mark of fire deck:
1x Deflagration
3x Flying Weapon
1x Wings
1x Owl's eye (or 2nd deflag)
Mark of death deck:
2x Arsenic
2x Spiders
1x Mummy
1x Eternity (or 3rd spider)
Oh if fire plays fractal phoenix and if we win, we might be able to fuse fractal and minor phoenix cards into our rainbow deck.