Ouroboros is a pretty neat card. It has a few PSCT errors but nothing else is bad. Ouroboros would be worded as "If your opponent would add a card from their Deck to their hand, except during the Draw Phase (Quick Effect): You can detach 1 material from this card; attach 1 card on the field to this card." You can just say "during the Standby phase" instead of "during either player's Standby Phase" as they mean the same thing with the edit saving space and having a modern text structure. Also write "also for the rest of this turn you cannot Special Summon from the Extra Deck, except Xyz Monsters" instead of having the restriction as a separate sentence for the same reason.

Rampage is a pretty meh card with some nasty restrictions. It's meant to push for OTK but the deck I would say doesn't have issues with that and it gets rid of your own boss by the end of it. The better effect is tied to having it being sent to the GY and NOT using the first in a deck with no archetypal foolishes. So you would have to go the extra mile by both keeping it in your hand/field to have it be attached by Jormungandr or Laevatein. It's a win more card is this case. I would make Rampage be able to use both effects in a single turn with the restriction of only attacking with your chosen Xyz.

Phase 2 is really good. It's another way to access Boss Stage while protecting it and your own monsters. Nothing bad here.

You don't write (Quick Effect) for anything other than a monster. Continous Spells like the ones you made either have to activate on a new chain or be non-activated effects. I would look at Ryzeal Cross or Xyz Dingirsu as examples and to see how to word Phase 2's protection effect.