Hey!
I found something interesting - the 
😝 Beat Me In A Game Of Steem-Monsters And Win A Free Card 😝
And the problem I see for such kind of Challenges is that you never know is the person online now.
So my suggestion is simple: need to implement the indicator - is the person online or not:
Or maybe even the special search list where you can search the users (whole users, not only like the single search in the Battle Log). And the list shows the users - like in the pop-up Player Profile window.
Yes, and you can also place the presence indicator in the Player Profile window.
Thanks for attention!
My different issues/suggestions to the Steem Monsters game:
Steem Monsters Tournaments suggestion: to add some more info & external checkbox column
Proposal of the pushable suggested price in the list for sale
The Tournament share button & add affiliate linking for this too
Steem Monsters Daily Quest 00:00:00 countdown issue - it needs to add auto-refresh the page
Tournaments suggestion - clickable urls in tournament description
Tournaments suggestion: to add some more info about the Completed ones
Steem Monsters: Monster Selection Mode needs some tunes
Steem Monsters site: I wonder does the date on site needs to be updated?
Steem Monsters Collection & Market tabs: lacks of pinned filter menu
Steem Monsters needs to improveslightly the Battle Statistics Table
pixelhunting issue for the Kiara Lightbringer card view)
About some more info descriptions about the catual actions on the main SM page
