Marina's guess has equal weight though. I'm still on the fence, I think it's more like
Entacmaea quadricolor than it is
Heteractis magnifica but it still really does have some vague ambiguity about it. That is the freakiest looking rim I've ever seen BTW, it looks like alien teeth. I should add neither my BTA's nor my ritteri have a rim like that (well I guess that goes without saying since I already said "I have never seen..." oops).
Here's the thing ... over time that ambiguity will lessen. So it will be interesting to see in a few month's time what we can learn.
I don't see any verrucae at all on that column. A little hard to tell since it has a slight wrinkled appearance instead of fully inflated smoothness. I was looking at my ritteri last night to see if there's anything I can extrapolate here. What I noticed is that I can't see the verrucae on the column by colour alone, since they are the exact same colour as the rest of the column. But by looking at the texture, you can see they are there still (so it's not as obvious as that picture of the pink base above, they are evident only if you really look closely enough).
The tentacle shape is also something that I'm noticing. In the second set of photos they widen a little, then are blunt ended with a tiny "nipple" at the very tip. This is something I've never seen on my ritteri. But I have seen it on BTA's.
In the end: my guess == BTA. With about a 60-70% certainty.
But like I said, maybe in a few months time it's possible we can take another stab at this and there will be something new to help with the ID.