In general, I would look at these two factors when looking to include cards not of your tribe's creature type: Is this creature so strong that it, on its own, is generally stronger than my tribal creatures when they are receiving bonuses and/or empowering my other cards
If you want a premium 30th display item, the FUTURISTIC BOX is the high-end choice
As you can see, theres a lot of good reasons to go and build an almighty Hydra deck, so we reckon you should just go ahead and do it
People love building around Sundial of the Infinite, and Time Stop is a super-powerful and popular effect in Commander because it can fizzle opponents mid-combo or mid-attack
Red-Eyes Zombie Dragon SR07-EN005 (YuGiOh Structure Deck: Zombie Horde | YuGiOh Cards) prices are based on the historic sales
Giving your team hexproof is a great roadblock for your opponents since they need two pieces of interaction to kill anything that's not Sigarda, but the card advantage is what you want