King led 5-4 from the previous session, but King's hopes of victory were threatened when seventh seed Allen produced some quality snooker early on.
Rattling in a few long-rangers, Allen settled the quicker and squared the match at 5-5, before sealing a second frame in quick succession to grab the lead.
The 14th frame proved an epic tussle, but one King seemed certain to have secured when he left Allen needing three snookers. But rather than throwing in the towel, Allen fought for the snookers he needed and sunk a stunning long brown as he opened a two-frame lead over King for the first time in the match.
But the world number 30 showed great mental fortitude to peg Allen back by claiming the last frame before the mid-session interval to close to 7-6.
Allen reopened his two-frame lead after the break, but King struck back with a tenacious 76 to close to stay in touch at 8-7.
King looked to be on his way to a big break, but got very unlucky when a superb pink failed to disturb the cluster of reds. But King kept his head and cleared up to level at 8-8.
With Allen struggling to reach the heights of early in the session, King marched on relentlessly, and booked a showdown against the winner of Ding Junhui's clash with Alan McManus in the last 16.
Mark King will carry a 5-4 lead over Mark Allen into the second session of a taut contest in the first round of the World Championship in Sheffield.
King trailed 3-2 and 4-3 after winning the first two frames of the match, but rallied strongly to stay in touch with the former world semi-finalist, snaring the final two frames of the session to lead 5-4.
A kick late in second frame proved costly to Allen as King returned to the table. He fluked the final blue before potting pink and black for a 2-0 lead.
World number six Allen reeled off the next three frames aided by runs of 83 and 66, but King showed tenacity to keep pace with the Antrim man as a closing 50 saw him dominate the final frame of the morning.
They play to a finish from 7pm (BST) on Monday evening with the first man to 10 frames booking their place in the last 16 and a match against Ding Junhui or Alan McManus.
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