Jayce, Defender of Tomorrow
Card Text & Abilities
[Empower] [2][A][A] ([2][A][A]: Empower me. Use only if not Empowered.) [1], [T]: Ready a gear. [Empowered][>] [1], [T]: Ready 2 gear.
Official Rules FAQ & Clarifications
1 Official FAQThere is a bit of a trick here, in that there are two important details to this question relating to dependent keywords:
Heimerdinger gains all activated abilities that have the [E] symbol in their cost, and he gains the entire ability, restrictions, costs, dependent keywords and all. In effect, Defender of Tomorrow’s ability that Heimerdinger is gaining is the whole line that says:
[Empowered][>] [1], [E]: Ready 2 gear.
Heimerdinger can gain this ability even if Defender of Tomorrow isn’t empowered because of that second point we made previously.
The key rule for this case is 727.1.b.1., which reads:
The Dependent Ability is present on the card for the sake of reference or evaluation until the Condition is met.
This means that the ability isn’t active and its text isn’t being processed yet, but other effects can reference or evaluate its text before the condition is met. Heimerdinger, Inventor is exactly one such effect.
Relevant Rules: 727.1., 727.1.b., 727.1.b.1.