Steve may notice that the sigil resembles the Arcana in some manner, but if he's familiar with the full Arcana in Abraxas, he'll realize it isn't recognizable as any of the signs in the deck. The symbol is painted with an odd thick black substance. Unlike the aged shrine, the symbol is not faded and looks new. Steve can recognize that sometimes runes in Solvunn, runes are painted using a similar-looking substance.

Morgana will detect magic, but she'll be detecting magic from all around them rather than strictly from the shrine as the entire cavern is shrouded in magic. However, she can sense that the shrine does carry a very old magic that's been there for a long time, possibly many generations.

If one of them knocks at the base of the shrine, beneath where the notch is located, it will sound hollow. There could be something inside if they find a way to open it, or it might just be empty.