Alien invader prongs

The ficus has been a bit thirsty, as you can tell by the leaves that have shrivelled slightly:

So I thought it's high time to first clean up the dead leaves, and also add water to the terrarium. The moss too seemed to be very dry (and I trimmed some of the long freaky moss prongs). I accidentally cut a little leaf, so I put it back into the soil, however it seems to be immune to decomposition:

This was all mid-September, and I was a tiny bit freaked out by these additional weird prongs:

Then, a little over a week ago, it started looking even more alien. The leaves were ok now (some browning?) but now these prongs looked sort of fungal. Don't like it.

A photo from today; that alien prong has grown further and is reaching the ground. I think I need to snip it before it consumes the terrarium!