I have a custom creature card in my cube. It’s a 0/4 with the text: “Rubblebelt Rioters gets +X/+0, where X is the greatest power among creatures.”
If it’s the only creature in play, it’s a 0/4. If it’s in play with a 1/1, then it’s a 1/4. Easy so far.
What happens if it’s the only creature in play and it has a +1/+1 counter on it? Is it a 1/5? Does it see that the greatest power is 1, so it gives itself +1/+0, then +2/+0, +4/+0 ad infinitum?
I don’t know of any real card with a similar static ability to check the rulings for.
Is it worded like that on any real mtg creatures? If so, check rulings on that creature. If not, maybe that’s why 😉
I couldn’t think of any. The real Rubblebelt Rioters has a trigger at the start of combat, and something with a static ability like Tarmogoyf never references itself that I’m aware of. I don’t think there is an official answer (because the ability doesn’t work when it’s worded this way) but I don’t know everything about Magic