Visual Arts:  Matthew Monahan, Sculpture and drawings, and African Masks and Fetishes, lent by Owen Hargreaves and Jasmine Albiston. Douglas Hyde Galleries 1 and 2, Trinity College Mon-Fri 11am-6pm, Thurs 11am-7pm, Sat 11am-4pm Until Mar 17 01-8961116

Local NewsMercedes Helnwein. Molesworth Gallery, 16 Molesworth Street. Until Feb 23 01-6791548

Matthew Monahan's exhibition at the Douglas Hyde Gallery makes a powerful impression. The visitor is greeted by a large group of strange, distorted but disturbingly human sculptural figures, mounted on roughhewn plinths, and accompanied by series of stylised figurative drawings rendered in a ritualised, obsessive manner. All of this seems thoroughly at home in the cavernous concrete space with its niches and alcoves. The work is also dizzyingly, exuberantly eclectic. So much so that the whole thing threatens to fall apart, both literally and figuratively. It doesn't, not only because Monahan goes for broke when half-measures would be fatal, but also because he has a real feeling for materials.

The plinths, for example, are unorthodox. Rather than being conventional, smooth, featureless blocks, they are clad in sheets of unadorned plasterboard, the crumbling gypsum of their untreated edges exposed. Then there are the sculptural figures, shambolic amalgams of various materials including "paper, wax, glass, foam" and what look like found bits and pieces. In some cases the resemblance to humanity is strong, but some pieces are so abstracted that, out of a group context, you would be hard put to read them as figurative at all.

Each, regarded as a potentially coherent, integral figure, is subjected to varying degrees of physical trauma: crushed, stretched, chopped, pierced, as though they are emblematic of sacrificial humanity. In terms of sources, the list of possible references is long and diverse.

The information leaflet, meanwhile, emphasizes the loftier concerns underlying the imagery, suggesting that it "embodies a powerful struggle between modernist and archaic belief systems".

There is in the work, we are told, a transcendent yearning for "a state of primordial wholeness." Maybe so.

Certainly, as well as European medieval sculpture, one is reminded of preserved bodies recovered from bogland or otherwise mummified, misshapen and discoloured by pressure and chemical processes, poignant and disturbingly immediate although they lived in the deep past.

It is hard not to think of more recent victims as well, bodies tortured, burnt and broken, more and more graphically depicted in news media and on the internet. There are also echoes of tribal fetish figures in the way Monahan uses his materials.

There is as well, though, a strong pop-cultural feeling to it all, drawing on the gothic and the grotesque as filtered through teen schlock horror in comic books and cinema. The imaginative worlds of Batman, The Lost Boys and Alien are all of a piece with Monahan's vision. The linear drawings of symmetrical, looming figures are part Mayan codices, part RH Giger.

In fact, the creepy vitality of Monahan's work depends on its wildly promiscuous infusion of sources and influences, and it is very compelling within these terms.

AS TO THE STRUGGLE between archaic and modernist "belief systems", the phrasing implies a relativistic equivalence while omitting any definition of the nature of the "systems"; the "primordial wholeness" is surely a myth. If there is a struggle enshrined in the work, it's a one-sided struggle. The obsessive patterning of the drawings and the pick-and-mix nature of the visual language of the sculpture indicate a commitment to a world of something like gothic fantasy. That is, the work is located within this composite imaginative world. When it comes to sacrificial victims, if we're going to pick sides in the debate, let's be with Spinoza against the barbarians.

The African Masks and Fetishes in Gallery 2 were not made as decorative objects. As an accompanying note observes, they don't depict or symbolise power, but embody it. They were produced with specific functions in mind and viewed and employed in that way. They are extraordinary objects and, while formal ingenuity was not integral to the making, their makers employed great formal inventiveness. The stark, forceful presence of the objects is related not only to their function within their societies but also to the way their makers set about solving the problems of conveying their function.

Mercedes Helnwein's drawings in her show Local News at the Molesworth Gallery are stylish and, for the most part, sinister. It is impossible not to see the links between it and the world of her father, Gottfried Helnwein: both make technically polished, photograph-like images, unsettling or disturbing to varying degrees.

In her drawings Mercedes Helnwein focuses on figures in interior settings. But these are figures in interiors as conceived by David Lynch, say. In practically every case there is something untoward and obscure going on.

On occasion the figures are stretched out on the ground as though they have fallen, but there is usually a theatrical element, as though they are playing at it. The lighting is invariably dramatic, with features strongly lit from below and casting deep shadows, for example. Apart from her considerable technical abilities, Helnwein's achievement is to string us along, so to speak.

There is a calculated ambiguity about her images. On the one hand they are dark and ominous and layered with menace, on the other there is the implication that it's all done with smoke and mirrors, it's only a game. Except that we can never opt for one or other option, and we are kept in a state of uncertainty.