No. 1 - Verzik Vitur
There is no debate here. Verzik Vitur is head and shoulders above the other bosses in Theatre of Blood, and that challenge is true in entry mode because of how many different mechanics are in play throughout.
The opening phase is simple. Use the Dawnbringer’s special attack to deal heavy damage to Verzik, and be sure to hide behind a pillar to avoid her magic charge attacks. Use Protect from Magic just in case you can’t hide in time.
In phase two, Ranged is recommended for entry mode, as it may not be quickest, but it is extremely reliable for learners. Protect from Ranged and avoid the urn bomb by moving away from your tile when she throws it, and be prepared to tank the blue electric ball.
When she spawns a Nylocas, simply avoid it, but if she spawns a purple one, kill it with a poison weapon, as this also does damage to the boss. When she spawns a red one, kill it; do not attack Verzik, as this will heal her. Once she reaches 35% health, switch to Protect from Magic.
Phase three can be kited with Ranged, and if you are simply doing the raid for the quest, that is the best way to approach it. She attacks with both Ranged (green) and Magic (blue), and you have more than enough time to switch your protection prayers once each attack is indicated.
She has four special attacks during this phase. The first one is a Nylocas spawn, which should again be avoided by continuing to move and kite the boss. The second one is her web attack, which is prompted when she moves to the center of the room. Simply run either clockwise or counterclockwise to avoid being hit by a web.
The third is her projectile attack, which can only be avoided by standing wherever the yellow pool spawns in the arena. And the fourth is the green ball attack, which will need to be tanked if soloing.
When she reaches 20% health, she spawns a purple tornado to chase the player around the room. Her Ranged and Magic attacks, plus her four special attacks, remain in play here, and she attacks at a quicker pace. But in terms of what you would expect from an enrage phrase, this one is relatively straightforward.
Overall, it’s an interesting and fun fight. It’s hard to rank entry mode Verzik Vitur against other quest bosses, since she’s not technically a quest boss. But in and of itself, this is a top 10, possibly even a top five, encounter on the road to the Quest Point Cape, in terms of raw difficulty.