Keeping with our example, pretend you decided you were impatient and moved from Trapped Entry to Oubliette
A Realm can host any number of creatures
Grixis combines red, black, and blue in what is commonly called a shard. These three colors allow for a weird mix of chaos and control strategies, upsetting your opponents' games while keeping your own on track as much as possible
I also like this in Hate Bears with enough bodies to pump up and get a Commander Damage kill with level 3
Im not aware of many, or any, equipment cards that have effects triggered by becoming attached or unattached (though Im sure there must be something), so I cant comment on how strong this mechanic will be in the long run
Time to shake out your bulk box