Cumulative Upkeep is a keyword ability.
It is a triggered ability that imposes an increasing cost to keep a permanent. At the beginning of its controller's Upkeep Step, that player must put an age counter on that permanent, and then may pay its upkeep cost for each time counter on said permanent, if they choose not to pay the cost they must then sacrifice it.
Andrew controls a Freyalise's Radiance with no age counter on it, and is moving into his upkeep. When Freyalise's Radiance's trigger resolves he must put an age counter then pay or sacrifice.
702.23. Cumulative Upkeep
- 702.23a. Cumulative upkeep is a triggered ability that imposes an increasing cost on a permanent. "Cumulative upkeep [cost]" means "At the beginning of your upkeep, if this permanent is on the battlefield, put an age counter on this permanent. Then you may pay [cost] for each age counter on it. If you don't, sacrifice it." If [cost] has choices associated with it, each choice is made separately for each age counter, then either the entire set of costs is paid, or none of them is paid. Partial payments aren't allowed.
- 702.23b. If a permanent has multiple instances of cumulative upkeep, each triggers separately. However, the age counters are not connected to any particular ability; each cumulative upkeep ability will count the total number of age counters on the permanent at the time that ability resolves.