How to Build Isaac?

Isaac tends to die pretty fast against Osh, and when Isaac dies, the team dies! So you really want him to have as much health as possible. Moreover it will make him ult more often by absorbing more magic damage.

In practice this means tree of wisdom 49, ascension V and a maxed Oliver patronage! Because of that I even advise making Oliver your first absolute star pet.

You should give him as little penetration as possible! No skin, no book artifact.

Why? This is because you do NOT want him to kill the spheres until he has gained four artifact buffs. Even if you just want to use Jhu (see below), this will still ensure a greater uptime with 3+ artifact buffs.

118 is optimal for either Lara, Jhu and Cornelius (with or without armor skin)! This is based on simulations with an optimal team, using the game engine itself, thanks to third-party tools.

Remember when I said armor penetration is dangerous? For the same reason you should get as little as possible, yet enough to give your damage dealers what they need to surpass Osh's armor.

• Jhu with Vex needs 3 artifact stacks of level 115

• Lara with Vex needs 3 artifact stacks of level 121 (when not self-buffed).

• Cornelius needs 4 artifact stacks of level 114

• Isaac needs 4 artifact stacks of level 112

So why is 118 optimal? There is a sharp difference with 117, not so much with 119, so I suspect it is the sweet spot for the whole team, where defense spheres are harmed enough with three artifact buffs to then be killed exactly by Isaac at the moment he gets the fourth buff.

Of course, for pvp, it would be better to have a higher level. But in practice it would rarely make a difference because mages have a low armor anyway. So a single stack should give enough penetration to the whole team. Even if they had an armor artifact on their side, Isaac ults fast enough to quickly gain a second stack, much faster than the enemies can increase their armor.

As long as you have not given him penetration, you should be relatively fine with attack power. I advise maxing his agility for armor, but not touching his physical attack skin and glyph - or just a bit.

Mine sits at 88k attack, and I am happy with him.

What if you screwed up and gave him penetration? Then no attack power for you, and you may have to sacrifice his agility (more premature deaths against Osh) or renounce high-scores.

Yes. Crucial for Osh, as Martha's artifact will save Isaac during the meteor shower. Useless for Maestro though. Also it is important for pvp.

Magic defense has zero effect when below the enemy penetration (see zerodef). And Isaac's magic def is way, way, below Osh's penetration. So there are two cases:

• Harmful if you have Cornelius in your team and you raised his weapon artifact (magic defense)

• Useless in all other cases

What about pvp? Magic defense slows down how fast you ult, in exchange for some survival. The pros and cons are circumstantial and debated among the community, but I personally advise you not to raise it.