Here's the cheese part:
In a 1 v 1 on Crucible - Erebus warps to portal flag (optionally uses invincibility item so towers don't hurt). The opponent ports or walks back to attack Erebus, who retreats by batwarping back across the gap. If opponent follows across the gap with warpstone then Erebus can warpstone back to portal flag and opponent is stuck waiting for warp or port cooldown. Erebus locks portal and teleports out. If opponent doesn't follow then Erebus can go farm until opponent is back at frontlines. Time it right, rinse, repeat, and you pretty much lock opponents to their base with minimal xp and grunts, while you continue to level...
Erebus will always have one warp more than the opponent, and on this map it can really make a difference
Edit: Cloak of Night + Warpstone + Batport exacerbates the issue - and yah, it's definitely worth getting Cloak and Stone for those lightning strikes