Storyteller Alison Williams-Bailey cuts an impressive figure as she parades into the room, her hair tumbling over the shoulders of her robe, an antler-topped staff clutched in her hand. She's here to share tales of Norse gods and legends – from Yggdrasil, the tree of life, to Ragnarök, the apocalyptic final battle. Her show divides into two parts; the first lives up to the spectacle of her entrance, the second sadly less so.

In the first, heavily-scripted segment, Williams-Bailey performs as though she's leading an ancient ritual. Commanding and mysterious, each word is chosen with care and loaded with densely-packed portent; and adding to the sense of ceremony, the narrative is punctuated by songs – some plaintive, some percussive, some akin to lullabies. The experience was disconcerting at first, as though I'd stumbled into the liturgy of a religion I don't understand, but as I relaxed into it I came to enjoy the feeling of majesty conjured by both the performance and the lore.

The second part is longer, and quite different: Williams-Bailey is off-script now, telling stories from memory and seemingly choosing her words as she goes along. And the tales now are hybrids, linking Norse mythology to the places and people of Sussex. At one point, for example, we hear a striking explanation of how the South Downs were made; there are several other references to specific places around Brighton.

On one level, this combination works. Setting stories in our own backyard illustrates how they first developed – not as a tale of somewhere far-off and exotic, but as a way of making sense of what we see at home. At the same time though, I found the unexpected juxtapositions nagged at my brain, especially when Williams-Bailey ramped up the humour by throwing modern references in.

Throughout the piece, Williams-Bailey maintains an enviable physicality, dropping down on her haunches or striding across the stage to illustrate a particular twist to the tale. And she's expressive as well; each time she looked at an imagined character or scene, I found it all but impossible to resist following her gaze.

But in the second, more improvised part, hesitations and digressions detracted a little too much from the main narrative thread. And at times I found it difficult to follow what was going on. There are a lot of unfamiliar Norse names to remember, and new characters appear all the time; I'd have appreciated occasional reminders of who was who, and where we'd met them before.

Overall then, the lower-key second part doesn't quite live up to the promise of the first. There was no particular explanation for the dramatic change in tone, and I wonder if Williams-Bailey is simply experimenting with styles; if so, then a filled-out version of the opening segment is a show I'd be delighted to see. In the meantime Creation Song is an entertaining way to spend an hour, and will introduce you to some intriguing stories – even if a few of the details do pass you by.