Scavenger's Talent

Gaining a level won't remove abilities that a Class had at a previous level.

Gaining a level is a normal activated ability. It uses the stack and can be responded to.

Scavenger's Talent's level 2 class ability will trigger when you sacrifice it. If you sacrifice other permanents at the same time, it triggers for them as well.

If you sacrifice a permanent as part of casting a spell or activating an ability, Scavenger's Talent's level 2 class ability will resolve before that spell or ability.

The creature card you return from your graveyard with Scavenger's Talent's level 3 class ability may be one of the nonland permanents you sacrificed.

Each Class has five abilities. The three in the major sections of its text box are class abilities. Class abilities can be static, activated, or triggered abilities. The other two are level abilities, one activated ability to advance the Class to level 2 and another to advance the Class to level 3.

There's no restriction on how many Class permanents you can control, whether they're the same or different classes. Each Class permanent tracks its own level separately.

Each Class starts with only the first of its three class abilities. As the first level ability resolves, the Class becomes level 2 and gains the second class ability. As the second level ability resolves, the Class becomes level 3 and gains the third class ability.