Currently, when you acquire Aghanim's Scepter after casting Doom, the doom duration on the enemy gets completely reset to 15 seconds if they get within range of Doom, no matter how much time was left on the Doom. This is currently abusable with Io's aghs Tether talent, which can be used to double Doom's duration without buying aghs.

Repro:
1. Cast Doom on an ene my (without aghs)
2. Wait some time
3. Before the Doom expires, get Aghanim's Scepter
4. Be sure the enemy is within the aghs duration-freeze range

Result: The Doom duration on the target fully resets, instead of just being "frozen". If the Doom had like for example 2 seconds left, its duration gets set back to 15 seconds, so if the enemy gets away from Doom, they are still doomed for 15 seconds, instead of 2.

Expected: Ideally, getting Aghanim's Scepter should not affect the current cast. Make the spell check for Aghs (or the aghs buff) upon cast, save it in a variable, and then have the spell check for that variable instead.