I think this does too much. Being able to cast this from your sideboard is, like, really, really, really strong, since it's essentially a free card. It kinda functions as a conspiracy card in a way, and we all know how busted the good ones are. (Not that they can't be fun, but still.) In addition you're getting at least 9 mana worth of effects by today's standards, not counting the casting from your sideboard ability. I'ld wager the card should cost more than that because being essentially a spell that doesn't cost a deck slot and doesn't rot in your hand.
I'ld be inclined to lower the impact by decreasing the effect to 2 of each. This would lower the net worth of the individual effects to somewhere between 5 and 6 mana, which means the desirable mana cost (to have that 2 in the cc as well) actually makes the spell more expensive than what you get out of the deal. In addition the spell becomes a lot less swingy, which is probably a good thing for a spell that doesn't take up a deck slot.
I do think the black effect is underwhelming and rather random and would probably change it to something different. Maybe -2/-2 to a creature, and then have the red effect deal 2 damage to a player or planeswalker? Discard two is a three mana effect, so that's probably too much.
i know it's absolutely absurdly strong, that was the intent. i don't think it's worth using the sideboard casting effect on something non-splashy and non-memorable though.
it's part of why i went with a 5c effect. i thought about making something even more deck specific but i also wanted it to be something people could easily remember, hence being based on the boon cycle from alpha.
which is also why it's got dark ritual on it, because that's the black boon. changing the numbers on the effects or changing away from dark ritual makes that no longer work.
but yea being able to cast it for 5 colors is the thing you have to draw and assemble, so in a way instead of being a free card, it is transforming all the lands in your deck into a free card if you draw certain combinations of them.
maybe the best choice might be . no matter what cost it would be, it'd require some serious testing to see how easy it is to cast in whatever environment it's in though.
i think the more interesting question than any of this is though: is it any fun at all?
there's issues with expectation, like being able to play it while your hand is empty can catch the other person off guard. i messed with requiring players to reveal it at the start of the game but i dont have a good way to word that that isn't hella verbose.
there's also just, the issue of taking away the surprise and randomness of drawing magic cards. i guess a lot depends on how easy it is to assemble 5 color lands in your environ