A vacuum filler pen with the ink capacity of an eyedropper filler!
I like pens with large ink reservoirs, because more is better, especially if I'm away from my ink stash. Eyedropper fillers offer the highest ink capacity, but...if you don't have a way to shut off ink flow between reservoir and nib unit, you run into "burping" issues, which can get very messy, especially if you can't see if there's ink in the cap. The solution was either a vac filler, or a "Japanese eyedropper", both of which have a plug attached to a rod that can be screwed into the opening between ink chamber and nib unit, sealing it off. My Opus 88 and Visconti Homo Sapiens have a total ink capacity of around 3.5ml. The Monster G5 has an ink capacity of 7ml. That's like 10 Standard International Short cartridges! That means most casual users might fill their Monster 2-3 times per year. Using a Fine nib, one complete fill lets you write 450 A4 pages, or about 54,000 words. Hopefully, you REALLY LOVE the ink you filled it with, because you'll be looking at that ink for a long, long time!
But not only is the ink capacity huge, the pen itself is pretty amazing, as well. The Kraken filling system, a clever variety of a vac filler system (with an improved shut off valve) that prioritizes ink capacity, is virtually unparalleled in modern pens currently on the market. The Ultem (or clear Acrylic) body of the pen is polished to crystal clarity, the metal is highly corrosion resistant titanium, and the #8 steel nib is smooth as glass.
I'm cheap, and boring, so I do most of my fountain pen writing on plain copier paper, which allows the ink to spread out, letting a Fine nib make a line like a Medium nib. I also like to use Pelikan 4001 Königsblau, because I got a good deal on the 1,000ml bottle of ink from my favorite online seller. The combination of cheap(er) paper and ink pairs really well with the Monster's #8 nib and feed; my Fine nib makes a line comparable to a Japanese Medium nib, while keeping the color richly saturated. Using standard European 5mm quad ruled paper, the nib writes thin enough to be perfectly legible. I do have to write a bit slower, though, because the generous ink flow also means longer drying times, and writing too quickly can cause smearing issue. That's a me-problem, not a pen-problem.
The nib itself is stiff, but very smooth, meeting or exceeding the smoothness of all of my JoWo #6 steel nibs. In my opinion, the combination of nib and feed make this one of the best general purpose pens you can buy, because it will work reliably on a wide variety of paper, and a wide variety of inks. As with all demonstrator type pens, avoid "high maintenance" inks, like permanent/document/waterproof inks (and Baystate Blue), because unless you're a professional writer/author, that ink is going to stay in your pen for at least a month, and your pretty clear tank may become stained permanently.
