Probably the worst card I've reviewed on this site since Dark Artist (was that 2 years ago?  wow, I'm getting old fast).  I ran Crystal Beasts for several years since they came out.  One well understood rule was that Rainbow Dragon is a terrible boss monster because it has steep summoning requirements and you need to wait a turn for its effects.  There's so many reasons why the Malefic version is bad.  First of all, Malefic Cyber End Dragon and Malefic Stardust Dragon both are superior to this card (no matter what deck you're using).  Second this card forces you to use Rainbow Dragon and there's serious potential draw probability issues.  It's a waste of deck space, for both this card and RD.  There's the attacking restriction, the field spell restriction and I can go on.  But seriously, there are so many better ways to put a big strong monster on the board.
 
1/5

I'm going to go with a 'no' for this card. Malefic Rainbow Dragon is a Level 10 Dark Dragon-type monster with 4000 Atk and 0 Def. It has all the same problems as yesterday's card with none of the benefits of being Level 8 or being a Blue-Eyes monster. Even worse, this one can't be Special Summoned by other ways. You would have to banish Rainbow Dragon from your hand or Deck. Regular BEWD is at least supported, but there hasn't been support for regular Rainbow Dragon or Crystal Beasts in general for years. Yesterday's card is splashable, this one is not. Avoid. 
 
Score: 2/5 Skill Drain makes it somewhat playable. 
Art: 4/5 Dragons are awesome. 
 
-WarlockBlitz

Continuing the Malefic theme, at least for another day, we look at Malefic Rainbow Dragon.  So first off, ALL the lovely liabilities and restrictions we saw in Malefic Blue-Eyes apply to this card, and in terms of one, specifically being able to remove the original from the Hand or Deck, to Special Summon this, is a blessing.  Playing the original Rainbow Dragon is quite a task.  Like it's non-Malefic counterpart, MRD has 4000 attack and 0 defense, is a Dragon, and again (go figure) of the Dark attribute.  Yesterday I said I wouldn't play Malefic Blue-Eyes in a Blue Eyes Deck, as I felt it took too much away from the Deck.  It just wouldn't fit.  Here, you could honestly try an MRD in a Crystal Beast Deck, if only because you're likely to have at least one Field Magic card in it.  Ancient City-Rainbow Ruins is actually a great Field Magic card (as far as they go).  The only problem here obviously, is despite the difficulty in summoning the original, the original Rainbow Dragon is FAR superior to MRD.  I feel being Level 11 (as opposed to Malefic Blue-Eyes 8) is a plus, in case you want to Synchro it into something (or some other insane hard to summon Monster) though that sort of defeats the purpose of bringing out a Malefic Monster, no?  It's stronger than yesterday, has slightly cooler art, but not really better.
 
Rating: 2.3/5 
Art:  4.5/5