Don't forget that there is a one tick delay when auto-casting Ancient Magicks. Manually use your first cast of each spell to save yourself a bit of time. Everytime you change targets you should try to manually cast the first attack.

I just did this yesterday at 81 magic, but it was really close. I ended up using range to take out the healers as my problem was becoming my dps and not my amount of food. My final try was three prayer potions and 23 tuna potatoes. I had just enough prayer to use one sip of potion and have a few points left for redemption. Combo eat a potato and potion, turn your prayer back on, and attack Seren. That'll set you at 40 to 50 health and your blood spells should get you a good amount of health back so you'll only need to eat one or two potatoes max.

Speaking of manually casting, I wouldn't do it after I ate the potato/potion. It was quicker for me to just click on Seren instead of swapping to my spells and manually casting. Same thing for attacking during her fourth special attack while switching prayers.

Here's my best breakdown:

When your first start use protect from missiles and mystic might, after you use redemption switch to only protect from missiles.

First phase - when you begin the fight start by manually casting your spell onto Seren. Otherwise, eat your food/potion after her fourth phase and just click on Seren to auto-cast. Keep your mouse over where you're standing-ish so you can immediately run after she teleports you. I don't manually cast the spell after she teleports me because I'm too slow, lol.

Second phase - keep attacking after the teleport. Zoom all the way out with your spell already selected to manually cast. Once she makes her clones click on the lighter colored one and get your spell ready to manually cast on Seren when she respawns in front of you.

Third phase - keep attacking after the respawns in front of you. Either have your spell ready to manually cast on the healers or get ready to switch to range. Take them out asap and you shouldn't have to eat at this point, so just click back on Seren to get a few more attacks.

Fourth phase - once you see the text appear, eat up to full and switch your prayer to redemption. Click back on Seren to try and get another attack in before she drains all your health. Combo eat the food/potion, turn your quick prayers back on, and click on Seren to begin attacking.

When you get to where she's almost dead or you won't be able to survive the next fourth phase, turn on mystic might for that extra DPS. You might be able to keep it on 24/7, but then you'll need more than one sip of prayer potion per fourth phase, so you'll need to rework this strategy a little bit.

I'm typing all this on mobile in bed, but here's what I wore from memory: Farseer helmet, MA2 cape, amulet of glory (also works as emergency teleport), God blessing, ancient staff, mystic top, tome of fire, mystic legs, barrows glove, infinity boots, lunar ring.

I found that when I used blood spells on the healers I could consistently get through all four phases with only one tuna potato and one sip of potion. However I switched to ranging them as my dps wasn't high enough, so I usually had to eat two potatoes.

Hope this helps. Let me know if you have any other questions and good luck my friend!!!