Rab's Mythic family of down jackets recently gained an ultralight addition, the Mythic G. With a whopping 1000 FP down fill, and a heat-reflective TILT lining that boosts warmth for no extra weight, this top-of-the-market jacket offers a surprising degree of insulating performance at an ultralight level of minimalism. It's the most expensive piece in the Mythic lineup as a consequence. Yes it's a niche product, and it'll certainly be a considered investment; but it is also really quite impressive.

This isn't the lightest offering in the Mythic range - that'd be the the Mythic Alpine Light, by a whisker. However the Mythic G's trump card is that it has among the best warmth-to-weight performance of any jacket Rab has yet produced, and with its higher spec innards it'll certainly be significantly warmer than the more affordable Alpine Light. Warmth-wise, it sits below the Mythic Ultra, a bulkier, heavier model we reviewed (and loved) last winter:

What's it for?

The Mythic Ultra remains our pick for serious cold - be that a frigid Alpine bivvy, a continental ice climbing trip, or a super-chilled high pressure Scottish winter mountain day. For those needing slightly less warmth at a lot less weight, the Mythic G is the one to watch. In terms of insulating performance we'd say it beats most ultralight down jackets into a cocked hat, and would doubtless hold its own against many midweight duvets several hundred grams heavier.

This jacket is ideal for ultralight backpacking, pretty much year round; I've used it on a chilly September summit camp where its combination of warmth and lightness were much appreciated. It's spot on for autumn hillwalking and scrambling too - on dry days at least. Weight-conscious mountaineers should also take a look. I doubt it has the oomph for full on winter in the Alps, but summer and bridge seasons ought to be well within its ability.

Weight

Rab's quoted weight is just 277g for a men's Medium or 252g in women's size 10. My men's Large is 295g, plus 7g for the nearly-not-there stuff sack; that's the sort of weight you'll barely notice in a pack, and it squashes down pretty small too. You can get lighter down jackets, but not by much, and I don't think there's any doubt that the Mythic G is exceptionally warm at this sort of weight. For reference - although they are not comparable - the Mythic Ultra is 506g size L.

Fit

All the models in the Mythic range come in both men's and women's fit - top marks to Rab for gender parity. I'm 1.83m tall, and reasonably chunky, and on me the cut in size L is spot on for a light down jacket, offering sufficient room to fit easily over a midlayer, but without excess space.

It's long enough in the body for snugness, with a hem well below the waist, and covering most of your bum. The active cut of the sleeves is really superb, with lovely free arm movement and barely a trace of hem lift when you're reaching up. If you want to climb or scramble in your down jacket, not just stand or stroll around in it, then this will be a major plus point. I don't think I've worn many down duvets this well cut. The simple stretchy sleeve cuffs will fit over a medium-bulky insulated glove, but struggle to cover a full-on gauntlet; I suppose that's consistent with the Mythic G's three-ish-season remit. 

As you might expect from a lightweight jacket, the hood is pretty simple. There's no adjustment, though you do get a bit of stretch and a semi-siffened brim that gives it some structure in the wind. It's not designed to pull over a helmet (you can at a pinch), but it's a lovely snug fit on a bare head. The high collar is good too, whether you're hood-up or hood-down, and its brushed chin guard is a nice touch.

Insulation

A down jacket is only as good as the stuff that's put in it, and in this case Rab have cut absolutely no corners, with a mega-lofty 1000FP European Goose Down fill. You get 127g of down in a men's size M, which at this quality is a meaningful amount for proper warmth while still giving you a compact and highly packable jacket. The down is held in stitch-through baffles. A standard construction for lighter weight down jackets, this may not be the most thermally efficient pattern, but has to be the lightest.

Added to this is the TILT (Thermo Ionic Lining Technology, in case you're asking) layer, a reflective coating 'painted' onto the inner side of the lining. A bit like a foil space blanket (yet silent, and fully breathable), this shiny side not only looks bling, but serves an important purpose, reducing your body's radiant heat loss by - Rab say - up to 30%, while contributing nothing to weight or bulk. This is zoned across most of the jacket, including the hood, and with exception only of the armpits, where you might appreciate a bit less warmth. In use I do think you notice the difference that TILT makes. 

TILT plus super-quality down is a formidable combination, accounting both for the jacket's high performance in its weight class, and of course its hefty price.

Fabric

Inside and out there's a tissue-thin 7D ripstop nylon, a super-light fabric that allows the down to fully loft. While it feels reasonably windproof, I don't think you'd want anything much skimpier on a down jacket. It's not going to take a lot of abuse, so regularly climbing with the Mythic G as your outer layer would seem a bit of a gamble. I've also noticed one or two escaped whisps of down. Fundamentally it's about saving weight.

Features

You would not expect a lot of features on an ultralight down jacket, and you don't get them here: a hem drawcord; two zipped hand pockets; and a robust YKK Vislon main zip; and that's your lot. I did wonder if the thin material might get a bit grabby in the zips, but this seems not to be a major problem. 

Ethics and environment

The fabric is fluorocarbon-free, while the down is RDS-certified.

Summary

The price seems more appropriate to an expedition-weight down jacket than an ultralight one, so the Mythic G will not be for everyone. However if you're seriously counting the grams and looking for the best warmth available at a minimalist weight, then this has to be pretty much state of the art.