Percentage movement speed stacks additively with other sources of percentage movement speed.
Upgrading Nomad's Medallion to Talisman of Ascension does not improve its ability to generate gold.
Talisman of Ascension's movement speed boost is especially useful for the advantage it provides a team when initiating or exiting a teamfight.
On Summoner's Rift, assuming Talisman of Ascension's user is within range of all minion deaths in a lane, it provides 8.3 gold per 10 seconds before the 35-minute mark. After 35 minutes, it provides 8.7 gold per 10.
On Summoner's Rift, assuming Talisman of Ascension's user is within range of all minion deaths in a lane, it provides 10.5 health regen per 5 seconds before the 35-minute mark. After 35 minutes, it provides 11.6 health regen per 5 seconds.
Talisman of Ascension provides the third-highest movement speedbuff available from an item when activated: 10% less than that of Mercurial Scimitar (however, Talisman of Ascension can affect multiple champions and lasts 2 seconds longer), and 20% less than that of Righteous Glory (which has the same duration but only works when moving towards enemy champions).
Talisman of Ascension contains two likely references to Dark Souls: "Praise the sun" is an in-game idiom, used by both the player and non-player characters; and September 22 is Dark Souls' release date.