League-of-legends – what is the meaning of circles near allied portraits in LoL

According to Riot's official description of League of Legends, available here:

League of Legends is a session-based, Multiplayer Online Battle-Arena game where rival teams compete against one another for victory on highly stylized battlefields and landscapes. Built by a veteran development team and the original creators of Defense of the Ancients (one of the world'­s most popular player-made mods), League of Legends combines elements of the role-playing and strategy genres with addictive battle action. League of Legends brings accessible, replayable and endlessly competitive gameplay that deepens with the player's commitment.

Bolded emphasis mine.

All of these could be variations of Greek letters (in particular: Ω Omega, Δ Delta, Θ Theta / Ο Omicron).

Quite possibly an inspiration for the design (with Nasus's background placing Nasus in what is roughly the equivalent of Ancient Egypt) are Egyptian hieroglyphs. Vertically aligned symbols and the use of underbars and simple shapes on a well-defined base (the individual blocks on the chain) is common there.

That said, these symbols don't match any commonly used characters or symbols, and barring any developer word we cannot - and should not - speculate on their meaning or actual origin.

The underlined Omega could be found in the Omega watchmaker's logo, the Delta might match the TYPO3 logo, and the underlined Omicron with a bold dot inside could be an eye, as used in various logos and logo concepts. The simplicity of these shapes makes them very common abstractions of existing logos, but the shapes themselves are generally not the actual logo.