Conquest of Elysium 3 is an old school fantasy strategy game. You explore your surroundings conquer locations that provides the resources you need. Resources needed vary much depending on what character you are, e.g. the high priestess need places where she can gather human sacrifices, the baron needs places where tax can be collected and where iron can be mined. These resources can then be used for magic rituals and troop recruitments. The main differentiator for this game is the amount of features and special abilities that can be used.
The game can be played on Windows, Linux (x86 and raspberry pi) and Mac OSX (intel and powerpc).
The beholder is probaly a bit more powerful than the other powerful monsters show here. It has cast spell** attacks. The ** means it will always use this attack and in addition to other attacks. So apart from casting 6 spells per turn it will also bite for 1-4 points of damage if it's in melee.