The name of that video slot is “Caligula” and its main attraction is its indefinite round of free spins, which is triggered by the appearance of 3 or more scatters represented with the head of a Roman centurion in any position on the reels.
During this round, you will see that above the reels, there are 15 pennants marked with multipliers that increase from x1 to x12 from left to right and also a circle at the end that encloses the word “End.”
Once triggered your round, you start to make your respective spins, then at any moment a scatter, but this time of blue color, may appear on the reel 5 showing a random number between 2 and 5, and that number will be the number of pennants that will disappear from left to right, then gains during your next spins, will be multiplied by the value of your current pennant and so on until reaching the “End.”
So, some of your wins during free spins will be multiplied initially by x1, then perhaps by x5 and during your last spins, they will be multiplied by a value between x8 and x12, so that the possibility of finishing your round of free games with a big win is quite high. In my case, my record of winnings during just one free round it was 103 times my total bet; good enough taking in mind I had already increased my bet a couple of times.
Sometimes you can spend hundreds of spins before getting a new round of free games, but I think it's worth bearing and waiting until this happens, first of all, being prudent enough when increasing your bet, something that certainly you have to do anyway in order to make the wait worthwhile.
Anyway, video slots of these characteristics tend to be quite volatile, and if your free round never arrives, most likely your session will end up with losses since the paytable in this slot is not as strong as paytables in other slots of few pay lines; however, I think “Caligula” is a slot that deserves a chance, especially if you're familiar with this type of slots.