Eye of Horus is basically a clone of Pharaoh's Tomb (from Novomatic).
In the bonus, the objective is to get expanding wilds - which will upgrade the symbols (left to right, one per wild) and award extra spins (1 spin for one, 3 spins for two and 5 spins for three). Additionally you can retrigger with 3 scatters for a further 12 spins.
It can get spicy if you get to the top level with a number of spins remaining (pays 50x per full line, 500x for the full screen; and enjoyable with the Novomatic music) - but of course if the wilds aren't landing, you could end up with peanuts or even zero because you are relying on the base mathematics of the game with few or no upgrades.
Or you can be me a few years ago... 9 spins for the top level and paid nothing on those spins
- but that is the nature of the game, can't argue with the mathematics.