To be equipped with Decaying dragon key. One cast of Sonar will immediately restore 80 Shields through the use of [Brief Respite] and the Double Augur mods. Through the Decaying Dragon Key, your Maximum shield is reduced to 75. As such, the sonar cast recovers full shields into overshields, and so it immediately recovers the full (1.3 seconds) of shieldgating Invulnerability.

Especially potent with hitscan weapons. With the 14x Damage Muliplier, you shouldn't have many issues killing things successfully, even in steel path content, and with arcane energize, your energy economy should be fine.
If in danger, just press 3.

If you still have energy issues, use Zenurik dash.

The [Xata]'s whisper is optional, but I've added it in [Preparation] for new [War] and the sentients to come. Already does quite well with basically deleting Acolytes.

Arcane Resistance in case there is a chance of toxin procs, since toxin bypasses shields, and toxin procs will otherwise just kill you. Honestly? Don't use this build on infested. Please. Just don't. And Think twice about using it for Toxin Liches and Sisters.

Otherwise can use Arcane Aegis for basically immortality while active.
[Intensify] is slightly more damage, but the difference in multiplier at that stage is somewhat miniscule, and the [Primed Flow] makes energy for repeated casts of sonar much easier through use of arcane energize.

Streamline is at 4, at 5 efficiency is slightly too high to regain full shields with one cast of sonar.
Use to bypass new lich/sister damage reduction formula.

Multiple casts of sonar can stack MULTIPLICATIVELY if the weak spots overlap, so if you can afford to cast it a few times for tougher enemies, go absolutely ham. Multipliers of x14 stacking multiplicitavely? MMmmmmmmm. With two overlapping instances, we're already looking at almost 200x the damage.

More comprehensive variants of upgrades for the exilus slot can be found here:
https://overframe.gg/build/186695/