From Rune Recall, head west and north up the trail of Mt. Sumter. As you journey upwards, you will come across a room that has an UP, DOWN and EAST exit. The Chromatic Dragon is 2 rooms to the east. The 2 rooms leading up to him are no-magic, so spell up and prepare for the battle prior to entering the path eastward.
The Chromatic Dragon is aggro, but doesn't always attack instantly. Like all dragons, he is immune to Bash, and also Negative damage. He loves to spam dracon breath attacks, so have shield block at the ready.
This is a very straight forward, standard fight. Flee out west to heal up. Very easy to spell up with FF, Poison, Web, but is immune to Irritation. Like most dragons, pierce is quite effective on him.
You sense the following: The Chromatic Dragon is a level 249 dragon aligned with Fallen-Gods, the worshiped Idols of Yore. The Chromatic Dragon has a Saving against Spells and Most Spell Effects modifier of 35. The Chromatic Dragon has a Saving against Breath Weapons modifier of 25. The Chromatic Dragon has a Saving against Petrification (i.e., Abjure, Kill, etc.) modifier of 5. The Chromatic Dragon has a saving against Magic Orbs, Staves, and Wands modifier of 5. The Chromatic Dragon is vulnerable to silver. The Chromatic Dragon is vulnerable to pierce. The Chromatic Dragon is immune to negative.